Mr Haw, 56, from Worcestershire, said that he was taken to nearby Charing Cross police station and released shortly afterwards without charge.

It is the first time he has been arrested since a high court ruling in July, which established his right to continue his one-man protest.

New legislation introduced this summer requires protesters to obtain police permission before mounting a demonstration within a mile of parliament.

But the court ruled that the requirement does not apply to Mr Haw, as his protest began before the law came into force.

After returning to his spot on the pavement, surrounded by banners and flags in Parliament Square, Mr Haw told PA: "I've been through this at great lengths with the police inspector and he accepts I've got the right to be here and to have friends keeping me company.

"He said he would inform his officers, but the message obviously hasn't filtered down to some of the constables on the beat.

"I was woken up at about 8am by a couple of them shouting at a young woman who was minding my stuff while I slept. They told her she was demonstrating and it was against the law, but she said she was just a friend of mine.

"I stuck my head out of my sleeping bag and said: 'Are you bothering this lady?' and, eventually, they arrested me for breach of the peace.

"I'm not breaching the peace. I'm fighting for it."

Scotland Yard had no immediate information on the incident.

Mr Haw began his lone vigil on June 2 2001, initially in protest at international sanctions on Iraq and, later, at the war and its aftermath.