Dr Jeffrey Cundy, co-author of the BMA's report, The Boxing Debate, published yesterday, said that the same abormal protein had been identified in the brain tissue of punch-drunk boxers and Alzheimer's patients.
Although young men may be apparently normal when they stop boxing, brain diseases associated with old age, including Alzheimer's, Parkinson's disease and senile dementia, can set in early - in their 30s and 40s, he said.
The report is the second on boxing to be published by the BMA. The first in 1984 was criticised by the British Boxing Board of Control because it took no account of more recent safety measures.
Drawing on the results of 11 surveys, The Boxing Debate concludes there is no evidence to suggest boxing is any safer today than it was a decade ago.
The report also dismissed claims that boxing could be made safer with headguards or shorter rounds. Evidence suggests the changes have a minimal effect - and in some cases might even cause more damage. The association called on the Government to set up an independent inquiry into the risks of brain injury in boxers.
John Morris, secretary of the British Boxing Board of Control, said: 'The Board have had no involvement or consultation over this report. Their concern is to destroy our sport, while we are interested in preserving it, with the safety of boxers very much in our minds.
'It seems very strange that an organisation announces its intention to call for the banning of a sport without giving the boxers or their organisation the chance to debate the issue.'
The Boxing Debate; British Medical Association; pounds 8.95.