Live television showed the protesters heckling Mr Blair

Police conducted checks on all visitors and delegates before giving them passes to the Brighton conference complex.

Anti-war protester Hector Christie said he was amazed the checks had failed to identify him as a "known activist".

One of a group of hunt supporters, Tom Leek, said that he had only joined the Labour Party two days earlier.

Mr Christie heckled the prime minister just seconds into his speech, shouting: "You have blood on your hands." He was bundled out of the conference hall.

Around 15 minutes later five hunt supporters set off personal alarms and began shouting at Mr Blair, before also being ejected from the hall.

Police arrested three people, all of whom are said to be Labour Party members. Sussex Police said they could be charged with disorderly conduct.

Passes

A force spokeswoman said that, as the protesters had conference passes, "there has been no breach of security".

"It is more a breach of trust between these individuals and the Labour Party," she said.

But a Labour spokesman said visitor passes were only issued after Sussex Police had checked the application forms.

"It is right that anyone who wants to come to conference can do so subject to the police conducting thorough background checks whether they are party members or not," he said.

Mr Christie said the police had failed to spot a "known activist with arrests and a short prison sentence".

Douglas Paton-Garner, who lives and works on Mr Christie's Tapley Park estate in Devon, said: "My five-year-old daughter could type his name into the internet and see all the protests he's been involved in."