Shares in Freddie Mac and Fannie Mae plunged in frantic trading yesterday in spite of attempts by US regulators to provide reassurance that the two government-sponsored mortgage financiers remained on a solid footing.

Shares in Freddie were down 22.03 per cent to $8 and Fannie's were off 13.78 per cent to $13.30 at the close in New York, their lowest levels since 1991.