Campaigners say the Terrorism Act is "overly-broad"

Lawrence White, from Notting Hill, west London, was told to move on or face arrest after the police officers searched his pockets and camera bag.

Civil liberties campaigners said it shows anti-terrorism powers are being used to intimidate the public.

People may be asked to move as part of security patrols, Scotland Yard said.

Mr White has written a letter of complaint about the matter to the Metropolitan Police Commissioner Sir Ian Blair.

Police powers

He said: "I was taking a few shots of the Houses of Parliament from the Albert Embankment on the other side of the Thames."

"I asked four officers if I could photograph them in front of the Houses of Parliament, but they said 'No, we're on anti-terrorist duty'."

He said as he walked away and took a few more shots one of the officers walked up to him and said "I want to search you under suspicion of being a terrorist".

Mr White said the officer cited Section 44 of the Terrorism Act 2000, which gives police powers to stop and search anyone if they suspect them of being involved in terrorism.

Shami Chakrabarti, director of civil rights group Liberty, said the act was "overly-broad" and one of the worst examples of "blank cheque" police powers.