The fathers' rights group linked to an alleged plot to kidnap Tony's Blair's youngest son is to disband in the wake of the furore over the affair, its founder member announced last night.

Fathers 4 Justice had earlier said the group was suspending its activities pending an inquiry into the allegations, reported in yesterday's Sun newspaper.

The group's leader Matt O' Connor told Channel 4 News that the group could no longer continue in light of the negative publicity generated by the allegations.

He said: "I regret to say that three years after starting the organisation we're going to cease and bring it to a close."

It was claimed that extremist sympathisers with the group had discussed kidnapping five-year-old Leo Blair.

Mr O'Connor said extremists had undermined the position and credibility of an organisation that had been "going along nicely".

''What these people are doing is undermining the very good work that people in this organisation have done."

He categorically denied he had handed the information to the newspaper as part of infighting within the Fathers 4 Justice group, which he insisted had been responsible for some of the most spectacular stunts the country has seen in years.

The group said officers from Scotland Yard's Anti-Terrorist Branch (SO13) had paid visits to some of its former members.

Both Downing Street and Scotland Yard refused to comment yesterday.

In a statement on the Fathers 4 Justice website, Mr O' Connor added: "I have three young boys myself and couldn't think of anything more traumatic for Mr Blair, his family and his son."

The alleged kidnap plot is thought to have got no further than the discussion stage.

Officers took the threat seriously, but privately police had doubted whether those allegedly involved were capable of carrying out such a plan.