George Robinson and Barbara Maines, south-west organisers for the Anti-Bullying Alliance - which receives a £500,000 grant from the Department for Education and Skills, said that their contracts had not be renewed because of their support for a "no blame" approach to tackling bullying.
Tony Blair had earlier told MPs that he was "shocked" by the no blame approach and "profoundly disagreed" with it.
Under the approach, bullies are encouraged to discuss their behaviour in support groups so they see the harm they have inflicted upon victims and change their behaviour.
The pair, who have worked with the alliance since its inception in 2002, said that the Prime Minister's office put pressure on Paul Ennals, the chief executive of the National Children's Bureau, which manages the alliance, to end their contracts.
A spokesman for Downing Street said that it was "completely untrue" to suggest it was involved with the termination of the contracts.
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