Health minister Ben Bradshaw accused the British Medical Association (BMA) of "misleading and mendacious" behaviour in amassing 1.2 million signatories to a petition calling for local GP surgeries to be protected.

The doctors' body rejected the claims and challenged the Government to forward any instances of inaccuracies or pressure on patients to support its campaign.

According to the union, GP practices will close as new "supersurgeries", housing GPs and other services such as blood tests and X-rays, are created. Its petition also calls on ministers to stop encouraging use of private firms to deliver primary care - something the BMA calls "creeping commercialisation".

Dr Laurence Buckman, chairman of the BMA's GPs Committee, is due to hand the petition in to Downing Street. In his speech to the BMA's Local Medical Committee (LMC) conference, he will say the script "will deliver a stark message to the Prime Minister".

"If the Government won't listen to you, their doctors, then surely it will listen to the 1.2 million men and women who call for a halt to the plans to promote the use of commercial companies in general practice.

"Voters don't want funding to move from GP practices to commercial companies who are accountable primarily to shareholders rather than patients. They want to be treated as patients, not customers. My message to Gordon Brown is this - 'Whatever you think of GPs, take note of what your electorate thinks. Work with us to improve the service, not against us, and ignore at your peril the wishes of the most important people in the NHS - the patients'."

Responding to the petition and the BMA's claims, Health Minister Ben Bradshaw said: "I am not surprised the BMA have collected so many signatures given the misleading and mendacious nature of their campaign. If I were to run a campaign making false claims that something terrible was about to happen, a lot of people would sign my petition too.

"I have written ... to Dr Hamish Meldrum of the BMA calling on him to disown the false statements being made and to condemn any kind of pressure being put on patients, when they feel at their most vulnerable, to support the BMA's misleading campaign."

Reacting to the minister, Dr Meldrum, chairman of BMA Council, said: "The BMA campaign material was carefully prepared with the help of patient groups and fully checked by our lawyers so I reject the claim that the BMA material is either misleading or mendacious."