In a speech at the BMA annual representative conference (ARM) in Belfast on Monday, Dr Porter warned that repeated funding cuts had left almost every hospital trust in England facing a financial deficit.
He slammed £200m public health cuts, highlighted that the UK spends a lower share of GDP on healthcare than the EU average, and pointed out that there are 'more health ministers in England than there are major emergency departments that met the four-hour waiting target'.
The BMA has adopted a neutral stance on the EU referendum vote later this week, but Dr Dr Porter said he could not remain neutral on 'fatuous and farcical claims' that the NHS would receive additional funding if the UK backed Brexit.
Dr Porter told the conference that this Thursday's vote would have 'profound consequences for healthcare in the United Kingdom'.
He said: 'We haven’t told BMA members how to vote on this issue. I, like you, have my personal views, and I think we can agree, as the BMA in Europe guide pointed out, on how many ways our lives are touched by EU membership. We were the first national medical association to have an office in Brussels and have lobbied on a wide range of issues for more than 20 years.
'Where none of us can be neutral, however, is in condemning the farcical and fatuous claims that have been a by-product of the political campaigns. We’ve warned before about politicians playing games with the health service. Here we see game-playing on a truly continental scale.
'That promise of billions of pounds of extra NHS funding if we leave the European Union. It’s beyond irresponsible. It relies on the unknowable assumption that the United Kingdom’s economy will be the same size, and the money would still be available. It is a promise that has been proven to be based on fantasy figures, but it is maintained as a slogan designed to deceive.'
On the government's approach to NHS funding, Dr Porter warned that ministers were 'in denial'.
'The chancellor says he has a "fully funded" plan for the NHS. But while he announced £10bn of new money in November, our funding report showed the real increase in health spending is less than half that. As for the rest, for the largest part of the unmet need, the plan relies on what he laughably calls "efficiency savings".
'We’ve seen those before. They are neither efficient nor are they savings. They are cuts. Year-on-year cuts to funding that have driven almost every acute trust in England into deficit. In total, more than £2bn in deficit, a 20-fold increase in two years. And this pernicious effect permeates every part of the United Kingdom.'
A DH spokesman said: 'We recognise parts of the NHS are under pressure as demand rises partly due to our ageing population, but this government is committed to the values of the NHS which is why we are investing £10bn in its own plan for the future — including almost £4bn this year.
'We continue to provide intensive support to improve performance and boost efficiency, but the NHS as a whole must now show tight financial grip and reduce the reliance on expensive agency staff.'