LONDON - A protester was bundled out of a British press ethics inquiry Monday as Tony Blair gave evidence, after bursting in and yelling that the former prime minister should be arrested for war crimes.

The man was dragged out by officials after he interrupted proceedings at the Leveson Inquiry into press ethics at the Royal Courts of Justice in London.

Well-spoken and dressed in a white shirt and light-coloured trousers, the protester appeared not from the public gallery seats but from the corridor behind where Judge Brian Leveson retreats to between sessions.

"This man should be arrested for war crimes," the man said as he gripped the judge's bench.

"JP Morgan paid him off for the Iraq War."

Leveson stood up, saying "Excuse me. Excuse me," as one security official restrained the man around the waist and struggled to drag him away.

"The man is a war criminal!", the protester yelled as another two security officials reached him, bundling him to the floor and then dragging him off.

Blair remained calm throughout the incident, with his chin resting on his hand.

"Who is he?" whispered Leveson. The lead counsel to the inquiry, Robert Jay, replied, "How did he get in?"

Leveson apologised to Blair and ordered an immediate investigation into the incident, which lasted no more than 30 seconds.

"I'm sorry for that, Mr Blair and I'd like to find out how this gentleman managed to access the court through what is supposed to be a secure corridor and I'll have an investigation undertaken about that immediately. I apologise," the judge said.

Blair, who is giving evidence under oath, said: "On the record, what he said about Iraq and JP Morgan is completely and totally untrue.

"I have never had a discussion with them about that or any relationship between them and Iraq."

The former premier added: "Part of the difficulty, actually, with modern politics -- and I say this not as a criticism of the media -- my experience of the reporting of these events is that you can have a thousand people in a room and someone gets up and shouts or throws something, that's the news.

"The other 999 might as well not have bothered turning up."

The protester identified himself as David Lawley Wakelin -- a documentary filmmaker who made "The Alternative Iraq Enquiry" -- as security guards took him away.

Blair continued his evidence once the man had been removed.

Around 20 protesters greeted Blair with an angry reception as he arrived at the court complex, waving banners reading "Troops home", "Bliar" and "Afghanistan out".

Blair sent British troops into both Iraq and Afghanistan during his time in office from 1997 to 2007.

After leaving office, he took a senior advisory role with US investment bank JP Morgan.

The incident was reminiscent of media baron Rupert Murdoch's appearance at a related British parliamentary inquiry into phone hacking at his now-defunct News of the World tabloid in July last year, which was interrupted when a comedian attacked him with a shaving foam pie.