Doctors will fight the government every day in the runup to the general election if it does not backtrack on changes to the NHS that have harmed patients, the British Medical Association's council chair has said.

In his speech to the BMA's annual conference on Monday, Dr Mark Porter said the changes had cut investment, fragmented care and prioritised the tendering of services to private companies. He also accused the government of "sly briefings" to the media, blaming doctors for every failed policy and criticising pay, thereby destroying morale in the NHS.

In a speech that sets the BMA on a collision course with the coalition over its reforms during campaigning for the 2015 election, Porter said it was not too late for things to change but warned that if they did not the association was "up for" the fight.

"We'll show the public that money is wasted on untested policies, not hard-working public servants," he said. "We'll show the public the care we already deliver out of hours, in hospitals and in general practice – and that we designed it and do it for them. We'll show the public the chronic lack of investment in emergency medicine, in general practice, in public health, in mental health, across the NHS. Who should the public blame? The people who work in the NHS, or the government that holds the purse strings? And with the general election just 10 months away, we could be fighting like this every day."

Porter said that under the coalition government the NHS had become obsessed with private companies tendering for services, describing the first full year of the Health and Social Care Act as a bumper year for multinationals and their lawyers and accountants, while making things worse for patients by fragmenting care among companies "eyeing up each other's business". He gave the example of Bedfordshire and Milton Keynes, where he said the management consultant firm McKinsey was carrying out a review of services at a cost of £3m as an example of "market lunacy". He said McKinsey had written to 500 providers, including one in the US offering "faith-based" healthcare.

Porter said he was angry at claims that NHS spending was protected. "The so-called efficiency savings are cuts," he said. "The experience of every healthcare worker, every doctor, is of having resources cut every year. We are seeing cuts that are driven by an uninformed and arrogant assumption that the NHS is bloated and inefficient."

He said savings should be made by not wasting money on management consultants or fragmenting care by opening the NHS to private bidders rather than by freezing the pay of medical staff.

The council chair described the government's promise not to impose change from the top as needlessly and recklessly broken, and asked: "Do you really want to be forever remembered as the government that spent five years breaking a promise, five years frog-marching the NHS towards fragmentation, five years attacking the morale of its staff and burning the rich fabric of goodwill?" Despite the savage criticism of its reforms, Porter insisted the BMA was ready to work with the government on improving patient care but warned that the Department of Health had to prove first that it had the best interests of the NHS at heart.

"First, you stop the screaming headlines and the starving of resources," he said. "Those sly briefings that blamed emergency medicine pressures on GPs, when the evidence said the opposite, and when practices are offering 40m more appointments than they did five years ago. Spreading the myth that consultants are not delivering urgent, emergency and acute care out of hours, when I and my colleagues are in hospital at 2 o'clock on a Sunday morning. What do you think that does for our morale? Finally, I say to the government: work with us, not against us."