Conservative leader David Cameron has said that nationalising Northern Rock would be "the most complete humiliation and failure for the government".
Mr Cameron was speaking on the Andrew Marr Show
Chancellor Alistair Darling told MPs last week that nationalisation is still an option but he would prefer a sale.
Speaking on the Andrew Marr show, Mr Cameron criticised the government's handling of Northern Rock.
He said a potential offer from Lloyds TSB for Northern Rock should have been considered more carefully.
Bank of England governor Mervyn King has said that the Lloyds TSB offer could not be accepted because it would have involved extending a £30bn taxpayer-backed loan to Lloyds.
A decision about whether to nationalise Northern Rock is probably only days away, according to the BBC's Business Editor, Robert Peston.
He added that a management team is in place if a commercial rescue package turns out to be impossible.
Mr Cameron also alleged that advice from City advisers to sell Northern Rock as soon as possible had been ignored for political reasons.
"I rather suspect that because of the planning for the early election the government didn't want to take a decision," he said.
He added that the main change needed to the way banks were regulated was a new Bank of England Act.
He said that the act should give powers to the Bank of England to intervene early if a bank was failing, instead of the current tripartite system that also involves the Financial Services Authority and the Chancellor.
He has also called for the governor of the Bank of England to be given a non-renewable term of office of eight years, instead of the current term of four years that may be renewed once.