The Liberal Democrats say it is the only answer. The Tories oppose it. The government is thinking about it. What would happen if Northern Rock were nationalised?
Will it soon be owned by the state?
What is nationalisation?
Nationalisation is quite simple. It means the government passes a law to take a business into state or public ownership.
By the 1970s, about a quarter of the entire UK economy had been taken into public hands as a result of governments, usually Labour ones, deciding that basic industries and the main levers of the economy should be owned by the public, not private share owners.
At one stage, the long list covered coalmining, steel, British Leyland cars, British Airways, airports, docks, shipbuilding, gas and electricity companies and the railway system.
What is the point?
Many of these industries had fallen into a decrepit state by the time they were nationalised. One reason for taking them over was precisely to keep them going rather than see them fold. That is clearly the goverment's aim with Northern Rock.
How easy is it to do?
In theory, and in practice, Northern Rock could be nationalised very quickly.
The government could simply put a one-line Enabling Bill before Parliament, stating simply that the bank would be taken over within 24 hours and giving the government all powers necessary to do so.
Has that ever been done before?
The most famous example of an emergency nationalisation was in 1971, when the Conservative government of the day, led by Edward Heath, took over Rolls Royce to stop it going bust.
The renowned maker of luxury cars and aero engines was regarded as a flagship manufacturer of the UK economy, but had overspent on developing the RB-211 jet engine.
What about banks?
Although a much smaller affair, the Johnson Matthey bank was nationalised for just £1 in 1984, again by a Conservative government.
Half of its loan book was dud and its debts outweighed its assets.
Although it was a tiny bank, it was thought too important to allow it to close down because of its role at the time in setting the price of gold, along with four other banks. It was later sold.
Just £1? What about the shareholders?
Good question. What about them? The government could decide to give Northern Rock shareholders almost nothing, or it could offer them a payment related to the stock market value of their shares, perhaps on the day before the nationalisation was announced.
The government would have some very big decisions to make and, hopefully, would have thought about them in advance.
Would it put in new management or keep the current lot, who have been recently installed themselves?
It would have to decide what it wanted to do with its new bank. Restore it to health and sell it later on; sell it at a more leisurely pace but without much effort to improve its finances; or run it off?
Running it off would involve closing it to new business, transferring the savers' accounts to another bank and then running down the mortgages over a long period of time.
Are there any other ways of taking over the bank?
The government is now the single biggest creditor. The bank clearly cannot repay the £25bn or so it has already borrowed.
So Alistair Darling could put in administrators and do a "pre-packaged" deal with them to buy the bank immediately, and cheaply.
However, the administrators might well want a government indemnity against being accused by other creditors of selling the bank too cheaply.
A normal administration, however, would be very complex and long drawn-out. In this situation, unless a buyer popped up quickly, it would almost certainly lead to Northern Rock being closed down and dismembered.
Any other tricks up the government's sleeve?
If it did not fancy passing a quick law, the government might think of using its reserve powers under the Bank of England Act of 1998.
This says that "The Treasury, after consultation with the Governor of the Bank, may by order give the Bank directions with respect to monetary policy if they are satisfied that the directions are required in the public interest and by extreme economic circumstances."
It might be arguable that taking over Northern Rock was "required in the public interest and by extreme economic circumstances", as the government has already propped it up by lending it very large sums of money.
So on the face of it, that one-line Bill in Parliament looks the easiest, cheapest and quickest method of doing things.