HOUSTON (CNNMoney.com) - Former Enron chief executive Jeffrey Skilling was in the hot seat Monday, trading barbs with the prosecution in what's shaping up to be a grueling cross-examination.

Right off the bat, government prosecutor Sean Berkowitz accused Skilling of "tailoring" his testimony to provide reasonable explanations for the company's questionable actions. Prosecutors also derided his lack of documentation or handwritten notes to back up his story.

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"I have nothing to hide, so it's not a question of tailoring testimony," Skilling said. "I will answer your questions to the best of my ability."

Skilling added, "I desperately want the truth to come out about what happened at Enron."

Skilling's cross-examination comes after he spent four days on the stand for the defense, taking sympathetic questions from his lead attorney Daniel Petrocelli. He was responding to accusations made by 22 government witnesses, many of whom were ex-Enron employees who cut deals with the government in exchange for their testimony.

On Monday, Berkowitz challenged the defense's use of jury consultant Reiko Hasuike, of RandD Strategic Solutions, suggesting that Skilling was using Hasuike's advice to help sway the jury in his favor.

"She consults on things like juror perception?" Berkowitz asked. Skilling hesitated and looked puzzled as to how to answer the question before responding that "she is helpful" in advising him on how to explain complicated financial transactions to jurors.

Tensions between the two escalated when Skilling discussed his views on the company's international assets.

Skilling has made no secret that he believed the company's international businesses were underperforming. He blamed some of that weakness on the regulatory landscapes of foreign countries, and even joked with the jury that those governments created operating environments similar to California's regulatory environment.

"You think this is funny? You're smiling," Berkowitz asked harshly after Skilling made his crack. Skilling's smile vanished abruptly and he looked hesitant about how to answer.

"I think the regulatory environment in California wasn't different from the regulatory environment in Brazil," Skilling said.

"You've previously made fun of California," Berkowitz pressed on, referring to a joke Skilling made in the past about the state's troubled energy market in which he compared California to the Titanic.

Skilling replied: "The state of California was unfairly targeting Enron."

Skilling testified that the company aggressively tried to sell its troubled international assets, including its Brazilian power plants, but was unable to reach a satisfactory deal. He said he eventually recommended to the board of directors that they hold on to the assets until there was a better price on the table.

But he denied the prosecution's assertions that the weakness in Enron's international businesses - and Skilling's inability to sell them - helped fuel the company's downfall. Enron went bankrupt "for reasons totally unrelated to this, Mr. Berkowitz," Skilling added in an exasperated tone.

The tension between the two grew stronger the more Skilling tried to defend his actions with regard to the international business. At one point, Berkowitz, frustrated at Skilling's lengthy explanations for his rationale regarding the international assets, cut Skilling short.

"I want you to answer my questions," Berkowitz said tersely. "I don't want to listen to speeches."

Skilling also stood by the company's use of the LJM partnerships – special purpose entities that the government contends were used to move millions of dollars in losses off of Enron's balance sheet – and denied that there were many complaints about the possibility of a conflict of interest due to former Enron financial chief Andrew Fastow's dual role as Enron CFO and general partner of LJM.

He said he didn't remember former employees such as Vince Kaminsky raising red flags over LJM at the time they were created. Kaminsky testified earlier for the prosecution that he warned Enron's executives that the LJM and Raptors financial structures were questionable but was ignored and later transferred to another division.

Skilling said he was surprised by Kaminsky's testimony that it wasn't very useful arguing with Skilling.

"That kind of hurt," Skilling said, adding that he and Kaminsky had engaged in many discussions over the years.

Skilling said he believed that LJM helped the company by providing an additional source of private equity funds but he believed Enron would have been fine without the partnerships.

"In retrospect, it would have been better not to have it," he said.

Skilling denied that he pushed Fastow to sell his share of LJM by 2001 because of concerns regarding the disclosure of Fastow's compensation. He said he never spoke to Fastow about disclosure concerns, despite an entry in his personal calendar that indicated that he had a meeting with the former CFO to talk about that issue. Fastow also testified that Skilling stated his concern over disclosure surrounding LJM.

"You have recollections that are different from your calendar entries?" Berkowitz asked. "Yes," Skilling replied.

"You have a difference of recollection with Mr. Fastow?" Berkowitz pressed on. "Very clearly a difference of recollection with Mr. Fastow," Skilling responded.

Berkowitz then asked if he had a difference in recollection from all of the other witnesses that testified for the prosecution, listing name after name. Skilling quietly responded yes to each name.

Berkowitz also accused the defendant of selling millions of dollars in stock based on inside information that Enron was in trouble.

Berkowitz asked Skilling if he was aware of the anonymous note that former executive Sherron Watkins sent to Enron founder Kenneth Lay in August 2001, outlining a number of accounting concerns that she believed would cause Enron "to implode in a wave of accounting scandals."

Skilling said he never saw the note until it was published in a newspaper a few months later, but that he disagreed with Watkins' assessment upon seeing the document. He said he had never been informed by Lay that the company was involved in any internal investigation or accounting improprieties. He also denied that his decision to sell stock had anything to do with accounting concerns or worries within the market - which would have amounted to insider trading.

He testified that he only sold 500,000 shares of stock because the Sept. 11 attacks shook his confidence in the market. And he insisted that he didn't hide his attempts to sell 200,000 shares - a sale that was never completed and that he originally said he forgot about during his testimony before the Securities and Exchange Commission - a week before the terrorist attacks. The government contends that Skilling was intent on unloading shares after resigning because he knew the company was headed for trouble.

Skilling said he didn't want Enron or the public to know about his sales because he was intent on maintaining his privacy after resigning from the company in August of 2001. He also said he didn't want the public to feel that there was a specific, negative reason for his decision to unload stocks.

He added that any stock he sold while CEO was done under a set approved plan that started in November 2000 and ended June 2001, when he felt the stock price had fallen too low. He also denied that he ever told his then-girlfriend Rebecca Carter or his ex-wife Susan Skilling to sell millions of dollars in stock in late 2000 after a deal to sell some of Enron's poor performing international assets fell through. He said he had no knowledge of those sales even as the prosecution presented evidence that both women had sold large bundles of shares, netting about $15 million between the two of them

And in a further painful and awkward attempt to refute the government's implication that he engaged in insider trading by informing his ex-wife and girlfriend to sell stock, Skilling joked to the jury "I was talking to my brothers during the break and they said, 'You didn't tell us to sell stock.'"

The joke fell flat on the court.

Both Skilling and Lay maintain that they are not only innocent, but that there were no crimes committed at Enron, with the exception of the actions of former Enron financial chief Andrew Fastow and a handful of cohorts. Furthermore the defense claims that the former executives that testified against the defendants did so out of fear of the government.

Lay and Skilling, who together face nearly three dozen fraud and conspiracy charges, are accused of lying to investors about the company's financial state while they enriched themselves by selling millions of dollars in stock.

Legal experts say the defendants could face 20 to 30 years behind bars if convicted of the charges. Lay will also face an additional trial for fraud once the current trial in Houston is over.

Enron was once the seventh-largest corporation in the U.S. It declared bankruptcy in December 2001, costing 4,000 employees their jobs and resulting in billions in losses for investors.

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