Liberal Democrat leader Nick Clegg is set to launch a fierce attack on "reckless and greedy" bankers as he seeks to capitalise on his party's remarkable surge in the polls.
Mr Clegg will use a press conference to highlight Lib Dem plans to break up the big banks to ensure that they cannot again "hold a gun to the head" of the rest of the economy.
He will point to the allegations about investment bank Goldman Sachs, which is being sued by the Securities and Exchange Commission in the United States over claims that it defrauded investors of a billion dollars, as evidence of the failure to clean up the system. The bank denies the charges.
"The allegations about Goldman Sachs are yet another reminder of how reckless and greedy the global banking industry had become," Mr Clegg will say.
"The great tragedy is that none of that recklessness or greed has yet been stamped out of the City of London, and it is costing jobs and businesses day by day."
He will argue that only the Lib Dems have the plans to create a "different kind of economy" which is no longer dependent on the City, while ensuring households and businesses can get access to the credit they need.
"We will break up the banks, to protect people's everyday savings from ever being used again to fuel the casino culture of the global financial industry," he will say.
"And to ensure that never again can the banks hold a gun to the head of the rest of the economy, we will impose a new banking levy of 10% on banks' profits until such time as they can be broken up, to ensure they pay for the guarantee they are receiving from the taxpayer."