A sign belonging to a branch of the Royal Bank of Scotland is seen in the City of London Jan. 19, 2009.

BEIJING, Jan. 20 (Xinhuanet)-- Shares in UK banks on Monday tumbled the most since 1985, despite a new 300-billion-pound (about 438 billion U.S. dollars) rescue package announced by the government to help troubled financial institutions, media reported.

Royal Bank of Scotland -- which earlier Monday posted a UK corporate record loss of up to 28 billion pounds (41.5 billion U.S. dollars) last year -- saw its shares plunge by 68 percent by 1620 GMT.

Lloyds Banking Group slumped 32 percent, Barclays -- which lost almost a quarter of its value Friday lost almost a quarter of its value on -- drop by 16 percent, and HSBC Holdings Plc was down by 11 percent.

By 1620 GMT, the FTSE 100 in London dropped by 1.6 percent, the DAX 30 in Frankfurt was down by 1.5 percent and the CAC 40 in Paris had fallen by 1.1 percent.

On Monday, the British government swooped in to boost its stake in troubled Royal Bank of Scotland to almost 70 percent and offered to insure banks against large-scale losses on risky assets in exchange for binding agreements to lend out more money to businesses and households.

The insurance scheme, announced by Prime Minister Gordon Grown and Chancellor Alistair Darling is, as they said, to protect banks from so-called toxic assets.

It was the second major British bank bailout in three months. Last October the UK government announced it would inject nearly 90 billion dollars of taxpayers' money into banks and lend them a further 350 billion dollars in return for preference shares and control over dividend payments and executive compensation.