The BMA manifesto published ahead of the 12 December general election calls for a 4% increase in overall NHS spending, alongside legislation to stop the pension tax crisis, better staffing and pay and a second Brexit referendum.
In a report on NHS winter pressure published alongside its 'Manifesto for Health', the BMA warns that 'trusts and GP practices are almost certain to endure the most pressurised winter on record'.
Pressures faced by the NHS over the summer were worse than even the worst-case scenarios forecast by the BMA, the association said.
It warned: 'Lack of recovery from summer, combined with other factors such as pensions taxation legislation forcing senior doctors to work fewer shifts to avoid large tax bills, and energy being spent on Brexit planning rather than winter preparedness, means the NHS is facing a perfect storm this winter.'
Factors such as particularly cold weather or a significant flu outbreak could trigger a winter 'substantially worse than our worst-case projections', the BMA warned - calling for urgent government action to prevent an 'unprecedented NHS crisis'.
BMA chair Dr Chaand Nagpaul said: 'Enough is enough. Right across the health service, trusts and GP practices will be bracing themselves for what looks set to be the worst winter the NHS has ever endured.
'Patients should not fear needing hospital care or being able to see their GP, nor should they have to accept that they may spend hours on a trolley in an emergency department, waiting to be treated.
'Similarly, staff working in hospitals and GP practices across the country should not be facing the daunting prospect of having to care for those patients in these relentlessly pressurised environments.
'This perfect storm is brewing alongside the upcoming general election and politicians should be paying close attention to the fall out of failure to invest in and support our health service for over a decade.'
The BMA chair warned that alongside the need for immediate support, the NHS needed more than just a 'short-term fix'. He added: 'This is about the current, and any future government, putting the NHS back on a sustainable footing, with capacity to meet the demands on its services.'
GPonline reported last week that general practice could face a devastating knock-on impact as pension taxes forced the majority of NHS surgeons to reduce their working hours. A recent dossier released by the Association of Medical Royal Colleges (AoMRC) revealed that medical specialties have been affected across the board, with some NHS services forced to close because of the staffing shortage.
GP workload has also been hit ahead of winter by rising drug shortages, with more than 100 medicines prescribed in primary care currently out of stock, while rising costs as practices are forced to prescribe expensive alternatives could hit other funding streams.