Banks were last night being pressed by the City regulator to raise as much capital as possible before an expected pre-market announcement this morning that could spell the end of Sir Fred Goodwin�s tenure at Royal Bank of Scotland.

Banks were last night being pressed by the City regulator to raise as much capital as possible before an expected pre-market announcement this morning that could spell the end of Sir Fred Goodwin's tenure at Royal Bank of Scotland.

The government agreed last week that it will pump as much as £50bn into UK banks to ensure they have a sufficient capital cushion to absorb rising losses on assets hit by the credit crunch. But negotiations continued over the weekend to finalise the form and size of the fundraisings.

"The figures are going up all the time," one source said.

Industry sources indicate that regulators' bargaining positions hardened over the weekend after warnings from key industry figures that banks needed to insulate themselves against any future bad news.

Dominique Strauss-Kahn, the International Monetary Fund's managing director, said that the global financial system is on the "brink of systemic meltdown".

Bank of England governor Mervyn King also told banks he wants them to ensure they can absorb all future writedowns as fears increase about the impact of investments such as credit insurance on their capital base.

Several UK banks, including RBS, HBOS, Barclays and Lloyds TSB, are expected to reveal their plans to investors before the market opens this morning. Among the issues is how much will come from the government and whether it will take seats on bank boards in return, an option Cabinet minister Hazel Blears said yesterday was under consideration. Some existing institutional investors are demanding the right to buy shares before the government takes a stake. There is also uncertainty over whether the International Accounting Standards Board will continue to require banks to hold assets at market value, rather than their estimate of the value, which affects how much capital they need to cover writedowns.

RBS is poised to make the biggest capital call. The company, tipped to raise anything between £2bn and £15bn, is expected to tell investors today it wants to raise a sum towards the top end of that scale. It is also expected to follow with news of board changes that could see Goodwin leave the bank he has headed since 1998. A potential successor is former Abbey finance director, Stephen Hester, chief executive of British Land who recently joined the RBS board as a non-executive.

RBS's market capitalisation slumped last week to under £12bn. This was less than it raised from investors earlier this year and left it ranked as Britain's fourth-largest bank, down from second earlier in the year.

HBOS, which insisted last night that its takeover by Lloyds TSB remained on track, had been expected to seek between £5bn and £10bn. If this all came from the government, it would leave HBOS majority-owned by the state. Lloyds TSB had been thought to need £3bn to £7bn. However, it now appears inevitable that the actual size of the fund-raising will affect the terms of the takeover deal.

Barclays is thought to be looking for £3bn to £5bn.