Speaking on CNN's Larry King talk show on Wednesday, Mr Clinton argued that the proposed deal offered a case study in the consequences of Republican economic mismanagement.
It was 'a horrible legacy of the Reagan years', he said, indicating that he would ban it if elected President.
'I've got real problems with it,' he said. 'We get no access to the British market.
'It's just an admission we allowed the American companies to get into terrible financial trouble.'
'So you wouldn't sign off on it?' asked Mr King. 'No,' was the uncharacteristically blunt Clinton reply.
The dollars 750m ( pounds 477m) BA-USAir link-up, still awaiting ratification by the US government, first entered the political arena during the final Presidential debate 10 days ago, when third candidate Ross Perot claimed it was another step towards the 'destruction of the US airline industry' and by extension a threat to the country's dominance of airliner manufacturing.
Mr Clinton's criticism, after his ambivalence over the planned North American Free Trade Agreement (Nafta) linking the US, Canada and Mexico and his accusations that the Bush administration had subsidised the export of American jobs, suggested that as President he would adopt a much harder-nosed attitude to US economic interests than his predecessor.
Mr Bush has stayed out of the controversy when questioned by voters. But supporters and foes of the BA deal have staged rival demonstrations at several of the President's airport campaign stops this week.
The row could also portend renewed US charges of 'unfair' subsidies from European governments to the Airbus consortium.
Mr Clinton claimed: 'They are driving McDonnell-Douglas to the brink of bankruptcy, killing workers in my home state and all over the country and even taking market share away from Boeing.'