US TREASURY secretary Hank Paulson is working on plans to inject up to $15 billion (£7.5 billion) of capital into Fannie Mae and Freddie Mac to stem the crisis at America’s biggest mortgage firms.

The two companies lost almost half their market value last week as rumours of a government bail-out swept the stock markets, hammering share prices around the world.

Together, the two stockholder-owned, government-sponsored companies own or guarantee almost half of America’s $12 trillion home-loan market and are vital to the functioning of the housing market.

The capital-injection plan is said to be high on a list of options being considered by regulators as a means of restoring confidence in the lenders. The move would protect the American housing market, but punish shareholders in both companies.

Under the terms of the proposed move, the US government would receive a new class of shares in exchange for the capital, which would be hugely dilutive to shareholders.

The potential rescue comes as investors are braced for more bad news from the financial sector. Citigroup is expected to reveal further writedowns of at least $8 billion with its second-quarter results, and Merrill Lynch is forecast to reveal writedowns of some $4 billion.

Both banks are expected to post sizeable losses for the second quarter, and reveal plans to sell off billions of pounds worth of assets.

A number of US regulators and politicians have been attempting to restore confidence in the two mortgage agencies.

Paulson and President George Bush stepped in to give vocal support to the two firms on Friday. “Freddie Mac and Fannie Mae are very important institutions,” said Bush, adding that he had spoken with Paulson who had “assured me that he and Ben Bernanke [the Federal Reserve chairman] will be working this issue very hard”.

Paulson killed off speculation that the government would renationalise the two agencies, a move that would have pitched the US public accounts into a new state of crisis.

However, Paulson pledged to support the two companies “in their current form”. He is said to have been concerned about the prospect of a rescue plan benefiting shareholders.

The capital injection would also see both lenders granted permission to use the Federal Reserve’s discount window - a short-term emergency funding source.

Freddie Mac has a $3 billion short-term funding line that comes up for renewal tomorrow. The short-term debt is one of the hundreds of funding lines that the two agencies use.

The funding lines allow Freddie and Fannie to buy mortgages from America’s commercial banks, which it then sells on to bond investors through securitisations. A government guarantee on the company’s debts allows it to raise money cheaply, making mortgages cheaper to finance for US banks.

Some in Wall Street believe a rescue plan may be announced ahead of tomorrow’s US market opening to calm nerves and support the debt auction.

Howard Shapiro, a Wall Street analyst at Fox-Pitt Kelton, said: “I think it will happen over the weekend. There will be government action but it will be far short of the dire scenarios that people are envisioning.” He said there was “no question” that the two firms were fundamentally sound.

He added that Paulson would have to move in order to “change the psychology” of the market and put Fannie and Freddie back on a stable footing.

David Buik, partner at BGC Partners, said: “These agencies are the backbone of financial society in the US. They simply cannot be allowed to fail, and the government won’t allow them to fail. Whatever the solution is to this problem, I can’t imagine it will be good for shareholders.”

He added: “In London we may see a dead-cat bounce on Monday, especially if we get a rescue. But that’s all it will be - shares may pop up 50 points or so, but then they will head down again.”

In the UK markets, HBOS will this week complete its £4 billion rights issue in a move that could see underwriters Morgan Stanley and Dresdner Kleinwort lumbered with more than £1 billion of the bank’s stock.

More than 13% of the HBOS shares in issue have been sold short by hedge funds - a bet that the bank’s share price will fall.

Bradford & Bingley will also put its lifesaving £400m rights issue to a shareholder vote.

Robert Parkes, UK equity strategist at HSBC, said: “It’s a seller’s market - we’re generally advising clients to sit on the sidelines until all the current issues blow over.”

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