Home Secretary Theresa May should take action against the extremist Muslims Against Crusades group, a Tory MP said after being threatened by the group at a constituency surgery in north London.

Up to a dozen protesters forced their way into a north London mosque where Mike Freer was meeting constituents, prompting officials to lock him in a private room for his own safety.

In a chilling message ahead of the incident on the group's website, they referred to Labour MP Stephen Timms - who was stabbed while holding a surgery in east London last year - warning the attack on him should serve as a "piercing reminder" to politicians that "their presence is no longer welcome in any Muslim area".

The disturbance at North Finchley Mosque on Friday afternoon began after internet messages posted on Facebook and the Muslims Against Crusades website urged supporters to target the Finchley and Golders Green MP, who had played a prominent role in the campaign against Palestinian activist Sheikh Raed Salah's visit to the UK earlier this year.

Mr Freer said there was a vocal demonstration outside the mosque as he began his surgery, but then a second group of people arrived and forced their way inside.

"One of them sat at a table where I was dealing with a constituent and was abusive," he said.

Mr Freer, a member of Conservative Friends of Israel, said he was called a "Jewish homosexual pig".

He was escorted by staff at the mosque to a locked part of the building until assistance arrived and described the incident as "uncomfortable".

But it was only when he was made aware of the website's reference to the attack on East Ham MP Mr Timms that he realised the potential danger.

Mr Freer said: "What I'm saying is the Home Office needs to be continuing to monitor this group and as soon as they overstep the mark then the full force of the law should come down on them."