He insisted no existing GP practices would be closed under the shake-up, which will lead to the creation of 100 new surgeries and 150 GP-led centres.

The Tories have claimed the plans will lead to the closure of 1,700 surgeries, and Mr Johnson said the BMA were speaking in "equally lurid and inaccurate terms".

The BMA has launched a Support Your Surgery campaign asking members of the public to sign a petition against private involvement in the NHS and expressing fears over the closure of local GP practices.

Writing in the Observer, Mr Johnson said: "Soon patients will benefit from changes that will see GPs offering evening and weekend opening.

"What is so dismaying is the way in which our plans for primary care and GP services have been the subject of gross misrepresentation.

"The Tories are claiming that our plans mean the closure of 1,700 surgeries.

"There is nothing further from the truth and it is extremely disappointing that the BMA would speak in equally lurid and inaccurate terms."

Defending the polyclinic plans, he accepted the proposals would be controversial but said decisions would be based on clinical evidence. "In some major cities, such as London, clinicians and managers want to go further than GP-run health centres and develop polyclinics - centres that offer an extended range of treatments. That might be achieved by bringing several GPs into a single building or they may be 'virtual', with GPs in their existing practices collaborating more closely."

He added: "The scaremongering and misleading claims we have seen from the Tories, and sadly from the BMA, should have no place in the crucial debate about our health service. The NHS is too important for that."