David Cameron has committed the Tories to imposing a new tax on banks as both main parties battled to convince voters they would claw back billions of pounds from the financial sector.
The Opposition leader said the US-style levy is needed to ensure taxpayers are repaid in full for the bail-out of financial institutions and protected from future collapses.
His firm pledge came amid renewed confidence of international backing for such a levy - although party sources indicated it would press ahead unilaterally with a more limited measure if not.
The Conservatives have not yet given any detail of how their scheme would operate. US President Barack Obama has signalled his intent to impose a "responsibility fee" and Sweden has introduced a levy.
Mr Cameron singled out the banking industry as one example of "vested interests" he is determined to confront and who he accuses Prime Minister Gordon Brown of failing to stand up to.