A fathers' rights group known for breaching government security said Wednesday it was disbanding after a newspaper reported that some of its extremist members plotted to kidnap Prime Minister Tony Blair's 5-year-old son.

The Sun newspaper reported Wednesday that extremist sympathizers of the group Fathers 4 Justice were hatching a plan to abduct Leo Blair and hold him for a short period to publicize the misery of fathers denied access to their children.

The newspaper said police carried out a security assessment after uncovering the plot, including what protection should be given to Blair's other children — sons Euan, 21, and Nicholas, 20, and daughter Kathryn, 17.

The British Broadcasting Corp. cited police officials it did not identify as saying the plan only got as far as the "chattering stage."

London police declined to comment on the report, and Blair's office said it did not discuss security issues.

Later Wednesday, Fathers 4 Justice founder Matt O'Connor told Britain's Channel 4 News program he decided to close the group because "extremists" had undermined its credibility.

"What these people are doing is undermining the very good work that people in this organization have done," he said. "I'm proud of the work we've done, but if we're going down this road with extremist elements then it's come to an end."

O'Connor, who claimed not to know about the alleged kidnap plot, said some members were kicked out last year because they supported "a more militant route."

"We do peaceful direct action with a dash of humor. We're in the business of uniting dads with their kids, not separating them," he said earlier.

O'Connor said he was aware of heightened police activity in recent weeks.

Anti-terrorist officers had visited former members of the group over the Christmas period, O'Connor said. Contacts at the Metropolitan Police had warned the group that armed police "were threatening to shoot people if they did anything in the region of Downing Street," he said.

Nobody has been arrested in connection with the alleged plot. According to The Sun, police foiled the plan at an early stage, and it was unclear whether the activists had even carried out reconnaissance of Downing Street.

Fathers 4 Justice has a history of breaching security at the heart of the British government during its campaign.

In May 2004, two activists hurled bags of purple flour at Blair inside the House of Commons chamber, prompting a security alert.

In April 2005, two members hurled eggs at Blair's car as he left a campaign rally.

An activist also has scaled the walls of Buckingham Palace dressed as Batman, while another member handcuffed himself to a government minister.