A dozen chanting men have stormed a London mosque to denounce Britain's principal umbrella group for Muslims.
Protesters disrupted the event at Regent's Park Mosque
The protesters at Regent's Park mosque said voting was against Islam and that Tony Blair "should go to hell".
Leaders of the Muslim Council of Britain tried to restore order but were drowned out by the demonstrators.
The group, believed to include former members of radical group Al Muhajiroun, said Muslims who voted would commit a crime against their own faith.
The council had been attempting to launch its manifesto for the general election.
The document does not back any particular party but seeks to set out the most important issues facing British Muslims.
However, within minutes of the launch starting the protesters barged into the mosque library, being used for the launch, and denounced the event.
A lead speaker, who did not give his name, said: "The MCB is the mouthpiece for Tony Blair.
Hit: Protester shoved MCB chief in the face
"The MCB can go to hell. Anyone who votes is kafir (an unbeliever)."
Council secretary general Iqbal Sacranie denounced the protesters, saying any decent Muslim would engage in proper debate rather than in headline-grabbing tactics.
One protester threw a punch at Mr Sacranie, but he was unhurt.
Other members of the MCB sat resigned, saying the demonstration would cause damage to the community.
Organisers of the event managed to restore order by using security guards to hustle the protesters out of the event.
Seeking to restore order Mr Sacranie said the demonstrators had proved that their own self-defeatist agenda would do nothing but damage British Muslims.
"These people are a minute group with the loudest voice.
"The responsibility is on us all to demonstrate what really concerns British Muslims. We must be aware of freak elements who have these views," Mr Sacranie said.
"I asked these people one question: is it part of Islam to behave in such a way? They did not answer me."
Prospective parliamentary candidates from the three main parties who attended the event denounced the demonstrators.
Ali Miraj, the Conservative candidate for Watford, said the Muslim community must not put its head in the sand.
It had to recognise "the growing cancer" of disenchanted young Muslims, he said.