Mark Lewis. Getty "This could be bigger than phone-hacking."

That's the view of the lawyer pursuing legal claims of up to £800 million ($1 billion) against Rupert Murdoch's News UK after Mazher Mahmood, the Sun on Sunday investigative reporter, was convicted of perverting the course of justice.

Seddons partner Mark Lewis was at the forefront of efforts to expose the News of the World phone-hacking scandal, but he believes Mahmood's conviction on Wednesday leaves News UK open to an even more damaging scandal.

Lewis has been approached by 25 people interested in suing News UK after they were caught up in a sting by Mahmood — also known as the "Fake Sheikh" — for the News of the World and Sun on Sunday.

Lewis' clients include former glamour model Emma Morgan and John Alford, a star of ITV drama "London’s Burning." He is also acting on behalf of former England football manager Sven-Göran Eriksson, who was targeted by Mahmood in 2006.

Michael Dodge / Getty Images Lewis said more evidence is emerging about Mahmood's methods and his conviction, in which he was found guilty of tampering with evidence in a drugs trial against British pop star Tulisa Contostavlos. It could be (another) watershed moment for Britain's tabloid media.

"There's a lot of money at stake for them [News UK]. There's a lot of reputational issues at stake for them. It potentially will open the floodgates," he told Business Insider.

"With phone hacking, all of the people didn't know their phone was being hacked. They might have lost some friendships, but they weren't suffering as a result of a printed story. This position is different because it actually entraps people. A lot of them ended up in prison, never working again, labelled as drug dealer, prostitute, or some sort of fraudster."

Mazher Mahmood. BBC Lewis said it was "very early" to say if the scandal could have ramifications for News UK's senior management, including chief executive Rebekah Brooks, who edited the News of the World from 2000 to 2003.

"I suspect that there would have been some people who thought it was all over, who might have thought: 'Oh God, it's coming back,'" Lewis said.

The lawyer is now working to process the claims and said it is too early to say how News UK will respond.

"It's always possible [News UK could settle]. There have been no offers yet, but we haven't made any claim yet, so I wouldn't expect there to be any offers. It's possible there will be a lot fighting before it is simply settled."

News UK declined to comment beyond a statement released after Mahmood's conviction. "We are disappointed by the news that Mazher Mahmood has been convicted. We do not have further comment at this time," a spokeswoman said.

She would not confirm if Mahmood is still employed by News UK.