Labour has promised it will impose a real split of retail and investment banking if it is elected.
Speaking ahead of his party's annual conference, Labour leader Ed Miliband explained he also intends to raise the top rate of personal income tax.
Mr Miliband claimed the Conservative-Liberal Democrat coalition has so far given in to lobbying in the UK's financial sector regarding how banks should be structured.
He said if the changes: "They can do it themselves - which frankly is not what has happened over the past year - or the next Labour government will, by law, break [them up]."
The current government has noted its actions on the matter will follow the recommendations made in an independent review by John Vickers, an economist at Oxford University, who is looking at how lenders should organise themselves following the global financial crisis.
Mr Miliband, however, said the industry needs real separation for a significant culture change to take place.
By Asim Shah