The first witness in Donald Trump's criminal hush money trial, former National Enquirer publisher David Pecker, testified on Tuesday that he used his supermarket tabloid to suppress stories that might have hurt Trump's 2016 presidential bid.

Pecker, 72, testified in a New York court that the Enquirer paid two people who were peddling stories of Trump's sexual misbehaviour but never published them — a practice known as "catch and kill."

"When someone's running for public office like this, it is very common for these women to call up a magazine like the National Enquirer to try to sell their stories," Pecker testified.

Pecker said the decision to bury the stories followed a 2015 meeting at which he told Trump that the Enquirer would publish favourable stories about the billionaire candidate and keep an eye out for people selling stories that might hurt him. He said he told an editor to keep the arrangement secret.

Pecker said the Enquirer paid former Playboy model Karen McDougal for her story of a sexual relationship with Trump in 2006 and 2007. He said he bought the story after Trump refused to do so himself.

"He said that anytime you do anything like this it always gets out," Pecker said.

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The Enquirer's parent company, American Media, said in 2018 it paid $150,000 for the story. Trump has denied having an affair with McDougal.

The tabloid also paid $30,000 for a story peddled by former Trump Tower doorman Dino Sajudin, who claimed Trump fathered a child with a maid who worked for him. The story turned out not to be true, Pecker said.

Both payments far exceeded the amounts the paper typically paid for stories, he said. "I made the decision to buy the story because of the potential embarrassment it would have to the campaign and Mr. Trump," Pecker said.

He is expected to testify further when the trial resumes on Thursday.

Pecker's actions helped deceive voters: prosecution

Prosecutors say Pecker's actions helped Trump deceive voters in the 2016 election by burying stories of alleged extramarital affairs at a time when he already faced multiple accusations of sexual misbehaviour.

They have charged Trump with criminally falsifying business records to cover up a $130,000 payment to buy the silence of porn star Stormy Daniels, who says they had a sexual encounter 10 years earlier.

Trump has pleaded not guilty and denies having an encounter with Daniels. His lawyers argue that Trump did not commit any crimes and only acted to protect his reputation.

The case may be the only one of Trump's four criminal prosecutions to go to trial before the Republican's Nov. 5 election rematch with Democratic President Joe Biden.

A guilty verdict would not bar Trump from taking office but could hurt his candidacy.

'Losing all credibility'

Pecker's testimony came after a hearing to consider prosecutors' request to fine Trump $10,000 for violating a gag order prohibiting him from criticizing witnesses, court officials and their relatives.

Justice Juan Merchan said he would not immediately rule on that request, but he appeared unmoved by Trump defence lawyer Todd Blanche's arguments that Trump was responding to political attacks, not intimidating witnesses.

"You've presented nothing," Merchan said. "I've asked you eight or nine times, show me the exact post he was responding to. You've not even been able to do that once."

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"I have to tell you right now, you're losing all credibility with the court," the judge added.

After the session, Trump repeated his claim that the gag order violated his constitutional free speech rights.

"This is a kangaroo court and the judge should recuse himself!" Trump wrote on his Truth Social platform.

New York prosecutor Christopher Conroy said Trump has run afoul of the order, pointing to an April 10 Truth Social post that called Daniels and Trump's former lawyer Michael Cohen "sleazebags." Both are expected to testify in the first criminal trial of a former U.S. president.

'He does it anyway'

Conroy said other posts led to media coverage that prompted a juror last week to withdraw over privacy concerns.

"He knows what he's not allowed to do and he does it anyway," Conroy said of Trump. "His disobedience of the order is willful. It's intentional."

The $10,000 fine sought by Conroy would be a relatively small penalty for Trump, who has posted $266.6 million in bonds as he appeals civil judgments in two other cases.

Conroy said he was not at this point asking Merchan to send Trump to jail for up to 30 days, as New York law allows.

"The defendant seems to be angling for that," Conroy said.

Blanche said Trump's posts were responses to political attacks by Cohen and not related to his former lawyer's expected testimony.

"He's allowed to respond to political attacks," Blanche said.