The former investigations editor at Rupert Murdoch's News of the World tabloid denied on Wednesday that his story allegedly exposing spot-fixing in Pakistan cricket was the result of phone hacking.
Giving evidence at the trial in a London court of former Pakistan Test captain Salman Butt and fast bowler Mohammad Asif, undercover reporter Mazher Mahmood said his probe was founded on "insinuating text messages".
Under cross-examination by defence lawyers, Mahmood repeatedly and vehemently insisted that voicemail interception - the illegal practice which led to the tabloid's closure - played no part in the story.
Saying his source would remain confidential, Mahmood told Southwark Crown Court it was someone whom he had known for years and had received payment for the tip-off after publication.
"They were insinuating text messages which showed these guys had been doing this for a long time," said Mahmood, who is testifying from behind a screen after the judge banned descriptions of his appearance because his security could be compromised.
"I can't go into the details of how the information was obtained," he said, to protect the source, adding that the defence lawyers were "assuming it's downloaded from a telephone" without the owner's knowledge.
"This story had nothing to do with phone hacking... I hope that the guys who are responsible for that go down," he said.
He said he "categorically" knew that the phone of Mazhar Majeed, an agent for several Pakistan players and the main subject of the investigation, had not been hacked, as the number was only known to very few people.
He added that he was "very sad" that phone hacking had overshadowed the good work the News of the World had done.
Prosecutors allege Butt and Asif agreed for no-balls to be bowled as part of a spot-fixing betting scam. The pair plead not guilty to charges of conspiracy to obtain and accept corrupt payments, and conspiracy to cheat at gambling.
Majeed and young Pakistan bowler Mohammad Aamer have also been charged with the same offences as Butt and Asif but are not standing trial alongside them.
Murdoch closed the News of the World in July as the phone-hacking scandal erupted following revelations that the weekly tabloid had hacked the voicemails of a murdered British schoolgirl.
Mahmood said he had never met or spoken to Glenn Mulcaire, a private investigator who was jailed for his part in phone hacking at the News of the World along with the paper's former royal editor, Clive Goodman.
Mahmood said he had received the initial information about the Pakistan spot-fixing claims from a source he had known for many years, who told him of the players involved.
The information the paper's team had was handed over to the police - with senior officer Cressida Dick present - by the News of the World's then-lawyer Tom Crone, Mahmood said.
He admitted that he had been to Pakistan after Osama bin Laden was killed in May this year but dismissed suggestions he had surreptitiously met Asif in the eastern city of Lahore as "ludicrous".
"I'm a guy who's received death threats from this. I have no desire to meet him," the reporter said. "If he's saying that, not only is he a match-fixer, he's also a liar."
Mahmood said that he had been doing stings for 20 years and criminals never invited him to their homes.
Having visited Majeed's home, he denied that this answer meant Majeed was not a criminal, calling him "an honest villain. The point being he wasn't going to rip me off."
He said that the 150,000 he gave Majeed was the biggest amount he had handed over to a sting target, adding that he himself would have come across as a somewhat "shady character", having such sums in a suitcase.
"We would not have paid that money if we were not convinced he was at it," Mahmood said.
He said Majeed had acknowledged that matches had been fixed in the past and would be in the future. "It was a massive story, it went all round the world."
Majeed claimed to know Geoff Boycott, Phil Tufnell, Mike Gatting, Imran Khan, Roger Federer and Brad Pitt.
Mahmood said the agent's boasts had to be taken with a pinch of salt but said some of Majeed's claims were true