A News of the World investigative reporter was today accused of being "economical with the truth" in his dealings with the police when they were investigating an alleged plot exposed by the paper to kidnap Victoria Beckham.
He was accused of not revealing the precise details of what he paid an informant for the story, published more than two years ago.
David Price, who is representing Romanian Alin Turcu in a libel action against the News of the World, said Mazher Mahmood had glossed over details of what he paid an informant for the story because he had been in a "tight spot".
The journalist - giving evidence on the fifth day of the trial - denied the charge, arguing that he had offered to chase up details for the police when he was being interviewed.
"Validating the cheque number and the cheque is certainly not being economical with the truth," he said. "I was called back to give a detailed statement. The whole story was being discussed in detail."
The court heard that the News of the World's informant, a Kosovan parking attendant called Florim Gashi, was paid £10,000 after the paper published its kidnap allegations in November 2002. Mahmood later told police Gashi had been paid "a few grand", Mr Price said.
Gashi had infiltrated an alleged criminal gang of eastern Europeans and it was his evidence, much of it caught on covertly obtained video and audiotapes, that was used by Mahmood for his story.
The evidence was passed on to police, though a subsequent trial of five men, including Turcu, collapsed in June 2003 when Gashi was deemed to be an unreliable witness.
Mahmood denied the informant was motivated by money and claimed he could have made far more than the £10,000 he was paid.
"There are lots of different types of informant," he said. "Gashi was never one to say, 'How much is this worth?'. I thought he was on a moral crusade, he never demanded money as a lot of people do: they are always ringing up saying, 'How much do I get? When do I get paid?'.
"The payment issue was largely led by myself because I was concerned about his welfare and I felt we owed it to him."
He added: "He could have demanded a huge sum of money. I would have gone to the editor [at that time Rebekah Wade, now the editor of the Sun] and I know the editor would have signed it off. There would have been no problem whatsoever. But he did not."
He could have earned £50,000
Mahmood said if Gashi had asked for £50,000, "he probably would have got it".
The court also heard that Mahmood's cousin, Mahmood Qureshi, who was recruited by the alleged gang as a driver, was paid £1,300 by the News of the World for his part in the investigation.
"Again, his motive is not financial," Mahmood said. "There are times when he comes down and acts as my minder for a day. He is happy to accept whatever he gets, frankly."
Mahmood also said that when it came to dealing with criminals, the paper had a policy of not offering "wads of money" to people to persuade them to commit crimes.
"We can't persuade people and we certainly don't offer wads of money and inducement. We try our best not to be agents provocateurs - that's a criticism repeatedly levelled at us.
"But if they [the criminals] are at it, it's possible to nail them."
Later, when Mr Price took issue with some of the phrasing of Mahmood's article, the journalist defended his language, including the statement that News of the World reporters "risked death". "If they [the alleged gang] had ever found out we were undercover reporters - Gashi, Qureshi and myself, these are ruthless people," he said.
"Our reporters daily risked death in all the meetings Gashi had with them. Even now he is living in fear. These people do bear grudges."
The journalist, who is said by his paper to have "put 133 crooks behind bars", added: "I get death threats all the time. You upset these criminals - it's not a good idea."
Mahmood today finished his seven-hour cross-examination. A number of other witnesses are still to be called and the trial likely to last the rest of the week.
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