Fathers' rights campaigners today said they had been warned to stay away from Downing Street amid fears of a plot to kidnap Tony Blair's youngest son.
According to the Sunnewspaper, extremist sympathisers with Fathers 4 Justice had hatched a scheme to snatch five-year-old Leo.
Officers from Special Branch apparently stumbled across the plan to attack the prime minister's family just before Christmas while investigating individuals on the fringe of group.
Matt O'Connor, a founding member of Fathers 4 Justice, said that they had been aware that a threat had been identified.
"There's evidence to support the fact that there was something going on, because SO13 officers (the Met's anti-terrorist unit) had visited some ex-members of the organisation over the Christmas period. That had set alarm bells ringing."
Mr O'Connor said that over the last couple of weeks, contacts in the Met had told them that SO13 "were threatening to shoot people if they did anything in the region of Downing Street".
However, the 38-year-old father-of-two insisted that they did not know the precise nature of the perceived plot, and condemned the idea of kidnapping "unreservedly". "We do peaceful direct action with a dash of humour. We're in the business of uniting dads with their kids, not separating them."
The Sunreported that there were no details of the alleged scheme to snatch Leo, but it was understood the men only wanted to hold him for a short period in order to highlight the plight of estranged fathers before releasing him unharmed.
A spokeswoman for the Metropolitan Police refused to comment on the allegations. A Downing Street spokesman also said they had no comment.
But Mr O'Connor confirmed they had been experiencing increasing trouble with a "dark underbelly" in the group. "There are some ex members who we turfed out last year. We had a bit of a clear-out in May of people who wanted to take the organisation on a more militant route.
"Other people wanted to go to the dark underbelly of the campaign. It's been a cause for concern for us for some time."