The meltdown in the giant US subprime mortgage sector gathered speed on Monday as shares in several leading lenders plunged and HSBC said it would take at least two years to fix its portfolio of bad home loans in the US.

Shares in New Century Financial, the third largest US subprime lender, plunged almost 70 per cent amid a sector-wide rout on Monday, as the company scrambled to avoid a bankruptcy filing following the disclosure of a criminal investigation into its practices.