The Conservatives have backed GPs' calls to be allowed to determine their own opening hours.
In a speech at the King's Fund on Monday, party leader David Cameron railed against polyclinics and urged GPs to sign a petition by think tank 2020health, drawn up in consultation with shadow health secretary Andrew Lansley.
Statements in the petition include: "We believe we should be free to determine the opening hours, size and locations of our practices, in response to our patients' needs, and object to being forced into polyclinics against our will."
Mr Cameron said a Conservative government would defend the values outlined in the petition, which also include support "for a level of remuneration commensurate with our responsibilities".
The party leader told the audience of healthcare professionals: "We want to work in partnership with GPs, not in conflict with them as this government is doing.
"So I urge GPs to sign up to this petition and ensure that the next Conservative government has the backing of the profession to modernise general practice in a way that works for the staff and patients of the NHS."
Health secretary Alan Johnson accused the Conservatives of being "more interested in ingratiating themselves with certain elements of the profession than in improving access for the public".
He said: "This is an astonishing admission by the Conservatives. They are now supporting a free-for-all on opening hours, which would see an end to the evening and weekend opening that has just been secured."
A Downing Street source said Number 10 was expecting to receive the petition in the next few weeks. "When we do, we will be asking Andrew Lansley and David Cameron if they are prepared to be honest with the public about the consequences of making GPs free to determine their own opening hours in terms of reduced weekend and evening access," he said.
"It is astonishing to see a Conservative leader siding so openly with the most reactionary GPs."
Mr Lansley said the party backed the provision of primary care services by secondary providers such as foundation trusts. But he said integration of services needed to be managed by a "proper independent regulator".
Speaking to HSJ, he criticised the forthcoming competition and co-operation panel, saying: "If you are going to have a competition authority, you have a competition authority, not a set of bods who can dip in and out of it.
"The Department of Health does not want to let go. They want to be able to distort the competition decisions to suit their own agenda," he added.