The Bank of England has announced a scheme to inject £50 billion ($100bn) into British banks as a means of easing the liquidity drought and stimulating mortgage lending.

In theory the package is unlimited since the banks are thought to need to raise £750 billion (($1.5tr) this year, but £50 billion is the estimate in the short term. This is billed as the biggest ever such package anywhere in the world.

The Bank will exchange its 9-month Treasury Bills, which are as good as cash, for the tainted debt obligations that many banks now hold. It will do so at around a 70/100 swap, what the markets call a “haircut”.

The haircut itself is variable according to movements in the markets, so taxpayers will be well insulated from large losses through defaults.

Instead of the normal auctions of Government Bonds on specific dates, this money will be available at any time, and will be confidential.

The only way outside observers will know if the scheme is working is by watching the LIBOR rate, which represents the rate at which banks will lend to each other in the money markets.

If it goes down from its present 5.9pc or so, the scheme will be having an effect on liquidity. If it goes up, which is unlikely, it’s back to the drawing board for the Bank and the Treasury.

Yet another huge loser in the American subprime mortage market is set to announce big writedowns next week.

Royal Bank of Scotland (RBS), Britain’s second largest bank, is understood to be seeking to raise capital from its shareholders in a rights issue thought to amount to £10 billion ($20bn), which is probably the biggest rights issue ever demanded in the UK.

The bank, which bought troubled NatWest and ABM Amro, has been running on low capital ratios for quite a while. It also has major exposure to subprime debt instruments. It has been linked with Spain’s Banco Santander for many years.

When such a major player is caught short like this, it brings home the extent and depth of the crisis in transatlantic financial markets, with all the knockon effects to the rest of the world.

Vince Cable, a spokesmen on Treasury matters who carries more weight than the Treasury these days, believes all the banks should follow the example of RBS, since they will need a great deal of liquidity from the Bank of England and that should be underwritten by shareholders, not taxpayers.

We await next week’s announcement, which will surely be leaked over the weekend.

As the first wave of the credit crunch plays itself to a messy conclusion, we are almost certainly now into its second leg.

Collateralized debt obligations (CDOs) may have been the opening gambit, but credit default swaps (CDSs) are the new kids on the block.

George Soros estimates that the value of CDSs now equals half of the U.S.’s household wealth, an almost unimaginable number — let’s call it $23 trillion. So what are CDSs?

They are hedges made by investors in case a company defaults on its debts. In effect you bet on a company failing to protect your investment in the event it does just that.

The problem arises when large numbers of companies go bust and the CDSs themselves become worthless since no-one can pay them out.

A CDS seller undertakes to compensate a buyer if a corporate bond defaults. Since there is no limit to the size of cover taken out, the value of CDSs often exceeds a company’s debts.

Moreover, many CDSs are bought with borrowed money so the infection of the system drives deep into the financial heartland like veins in a blue cheese.

As defaults rise to unprecedented levels, so the whole ricketty system threatens to collapse.

Another nightmare to look forward to.

It’s official! Well, almost. The IMF, that august body which presumes to overlook the “world economy”, has used the “T” word.

The International Monetary Fund says that losses from the credit crunch by financial institutions worldwide are set to reach $1 trillion (£500 billion), threatening severe economic fallout.

The Fund says, “At present, the issuance of most structured credit products — instruments that pool and tranche credit risk exposures in various ways — is at a standstill and many banks are coping with losses and involuntary balance expansions.”

On the day when the UK’s biggest mortgage lender, the Halifax, reported a staggering 2.5pc drop in house prices in March alone, the IMF warns governments, central banks and regulators that they now face a test of their mettle unique in modern times.

In its twice-yearly Global Financial Stability Report, the Fund remarks, “The critical challenge now facing policymakers is to take immediate steps to mitigate the risks of an even more wrenching adjustment.”

The danger is that the escalating losses of banks, combined with credit market uncertainties, could generate a vicious downward spiral as they weaken economies and asset prices, leading to higher unemployment, more loan defaults and even deeper losses.

“This dynamic has the potential to be more severe than in previous credit cycles, given the degree of securitisation and leverage in the system.”

The report indicates that this downturn is about more than just liquidity, as some commentators are still arguing, but is rooted in “deep-seated fragilities” among banks with too little capital. This “means that its effects are likely to be broader, deeper and more protracted.”

In addition, “a broadening deterioration of credit is likely to put added pressure on systemically important financial institutions.”

Moreover, “The corporate debt market appears vulnerable as default rates are set to rise.” Loan defaults on junk bonds (high-risk corporate debt) have already begun to increase in both the US and Europe, which is “an area of specific concern”.

“This leaves financial institutions, most recently hedge funds, vulnerable to mutually reinforcing funding and market liquidity spirals, in which investors sell assets to meet funding requirements, creating price declines, a loss of confidence, and further funding pressures.”

The IMF advises : “National authorities may wish to prepare contingency plans for dealing with large stocks of impaired assets if writedowns lead to disruptive dynamics and significant negative effects on the real economy.”

Which broadly means that the situation is bad and getting worse, and the worst-case scenario may be just around the corner.

Macroeconomics was never so fascinating, and never so scary.

Read the report here.