Charity Sweet, 40, and a mother-of-three, was holding a copy of Thursday's edition which carried the headline: "Warning: if you read this newspaper you may be arrested under the Government's anti-terror laws."

Inside was an article reprinted from Vanity Fair magazine which ran across the first three pages of that day's issue of the newspaper. The article, by the writer Henry Porter, accused the Blair Government of a sustained erosion of civil liberties.

As she sat outside Downing Street, Ms Sweet was approached and questioned by a police officer. When he had finished his inquiries she was astonished to be handed a form detailing the reasons for his interest which included "reading today's Independent".

Earlier this month, Steven Jago, an accountant and also an anti-war protester and friend of Ms Sweet, was arrested by police and later charged under the Serious and Organised Crime Act. He had been carrying copies of the magazine which were confiscated by police.

On Thursday afternoon, after seeing The Independent had reprinted the article, Ms Sweet decided she would demonstrate her solidarity with Mr Jago and went to Downing Street to find him. Unsuccessful, she bought a sandwich and decided to eat it while sitting down under a tree near the gated entrance to Downing Street and reading the newspaper. She was also wearing a sign around her neck warning against bullying. After some minutes she was interrupted and questioned by a Scotland Yard officer.

Ms Sweet, from Chatham in Kent, said: "It was intrusive and ridiculous to think that I could not sit there and read the newspaper when I chose to. I don't have any issues with the officer himself, he was perfectly polite and just doing his job. He asked me who I was and what I was doing there.

I told him the publication of the article was history in the making and I could not think of a more appropriate place to sit down and read it. I don't think I was causing a problem for anybody." She was not cautioned or arrested.

As is normal procedure, the officer handed Ms Sweet a form which set out why a particular person is stopped and, as can happen, searched. Under the section requiring a description of what the person stopped had been doing, the officer wrote: "Sitting outside D Street with Notification Around Neck about Bullying. And Reading Today's Independent."

Ms Sweet was allowed to continue reading The Independent. She left soon after, found Mr Jago and they went to sing protest songs and hymns outside the Palace of Westminster.

Ms Sweet's interest in the Iraq conflict stems from the fact that her first husband was an Iraqi Christian and their daughter, who is 18, is therefore half-Iraqi. She said: "What has happened there since the war is genocide. Life under that terrible dictator was actually far, far kinder and that is a very sad state of affairs." Originally from Canada, she has been living in the UK since 1991 and has two other children, a girl aged seven and a 13-year-old boy.

She has been cautioned once before and was present when Mr Jago was arrested. "I don't want to do things that get me arrested, because I am a mother and sometimes I have my young children with me," she said. "I am into building bridges, not burning them down."