According to research by Moody’s, the credit ratings agency, the UK’s banks and building societies could absorb a 20 percent fall in house prices in a year without further denting their capital reserves.

The study, set to be published on Friday, comes as shares in Britain’s largest lenders continue to slide, raising fresh concerns that the investment banks that have underwritten the rights issues for Royal Bank of Scotland and Bradford and Bingley would be left holding a substantial proportion of the new shares.

Now at their lowest level for a decade, RBS’ shares have slipped 2.6 percent to 231.75p. Meanwhile, B&B’s shares dropped almost 7 percent to close at 90.5p, which is just 8.5p above the 82p underwriting price for its £300m rights issue.

The weak share prices reflect growing concerns about the impact of the slowing UK economy and falling house prices on banks’ profits. Investors are starting to believe we could see a repeat of the housing slump in the early 1990s.

The Moody’s research suggests, however, that even if house prices were to fall by a fifth, most banks will have sufficient capitol reserves. A 50 percent fall in house prices however would leave many banks needing fresh capital.

Elisabeth Rudman, a Moody’s senior credit officer said, “We found from our stress tests that the mortgage lenders do have a considerable ability to absorb a substantial downturn in that market.”

As reported late last week, RBS, HBOS and B&B have launched rights issues to rebuild their balance sheets, although these capital raisings have mainly been designed to boost reserves after the banks suffered losses on investments linked to the US mortgage market.

Moody’s said it couldn’t rule out further writedowns at the UK banks until house prices had stabilised.

Falling share prices of RBS and B&B have confounded bankers, who priced the rights issues at a heavy discount in order to increase their chances of success.

The sell-off also hit banks that have resisted the pressure to raise capital. Barclays shares, on Thursday, fell 9.75p to close at a five-year low of 377.5p.