Running the banks has been rather like herding cats. Ministers were right to rescue Royal Bank of Scotland, Lloyds, HBOS and Northern Rock from a solvency crisis that could have had devastasting consequences for the wider economy. But they are now looking for the exit. Selling at least some of these institutions back into private hands before the election would rid Gordon Brown of this turbulent priesthood and let him claim to have ended the banking crisis.

A rushed sale, however, could have nasty consequences for economic growth. Ministers have a clear choice. They can either run these banks to maximise lending and help to reflate the economy, or fatten them up to recoup some of the taxpayer’s investment quickly. The choice is essentially between a long-term gain to the economy and the short-term financial benefit of getting at least some liabilities off the books.

The Government has sent mixed signals about which route it favours. It has loudly urged RBS and Lloyds to keep credit flowing in the economy. But it has also quietly told its advisers to find a way of getting Northern Rock back into private ownership before Christmas, apparently with both the full support of Lord Mandelson and to the fury of the Shareholder Executive. It has structured a gargantuan salary package for Stephen Hester, the new RBS chief executive, which will reward him substantially if he can raise the bank’s share price. A higher share price would be a precondition for any successful sale. Tesco and Virgin may be among the bidders.

Selling off the pesky banks would take a weight off ministerial minds, please minority shareholders and slash the size of the psychological bill hanging over taxpayers. But it would also entail shrinking the banks to maximise profits. This would mean refusing credit to all but the safest borrowers, charging punitive interest rates and running down the balance sheet. With many businesses still suffering acutely from lack of credit, this is the wrong time to encourage big lenders to withdraw from anything that looks remotely risky. Britain no longer has a solvency crisis, but it still has a lending crisis. Tackling that should be the Government’s priority.

The other problem with a hasty sale is that it is unlikely to be a good deal for the public purse. With stock markets still recovering, and none of the state-owned banks yet on a really stable footing, any kind of float looks risky and any private buyer would be likely to strike a hard bargain that would leave the taxpayer holding a rump of bad loans.

While the financial calculations are bedevilled with complexity, the political calculation is much clearer. Messrs Brown and Mandelson no doubt relish the prospect of the headlines that would appear alongside any announcement that the Government had recovered billions of pounds from a sale. They would hate to see a future Conservative administration take credit for denationalising the banks and restoring the economy. But reflating the economy must be an imperative, no matter where the gains fall politically.

This newspaper supported the Government’s bank rescue. But the reason for recapitalising the banks was so that they could start lending again. Herding cats may have been a pretty thankless task, but abandoning the task too early will give the wrong cats the cream.