Boris: Bankers have only themselves to blame for super-tax

As the City reacted in horror at plans for a punitive super-tax on bonuses being drawn up at the Treasury, the Mayor said there should have been more self-restraint.

Mr Johnson has been the bankers' sole senior political champion in recent months as ministers and Opposition spokesmen vied to condemn City greed and the return of the bonus culture.

But a spokesman for the Mayor said: "He is disappointed in them in that he has made the case and they have not helped themselves. He still thinks that the sort of tax being talked about is a bad move. The Mayor is, in principle, opposed to one-off, random, short-term measures that appear politically vindictive and are timed late in the electoral cycle, that could have damaging consequences for the economy, and particularly London, for years to come."

In the City, a backlash was growing over Alistair Darling's plan for the super-tax on banks paying huge bonuses. Bankers said it would drive ­talent abroad and might be illegal under human rights laws.

The Evening Standard understands that the Chancellor is considering a one-year tax on banks rather than bankers themselves, though he has ruled out a simple windfall tax on profits. His proposals would target financial institutions whose discretionary bonus payouts are way above a level deemed acceptable.

It would not, however, single out only those such as RBS that have been bailed out directly by the taxpayer.

Euan Sterling, of Standard Life, said: "These one-off taxes are usually seen for what they are, fairly short-term and populist measures that do little to change behaviour. It would do nothing to increase investment in the country, nothing to increase the flow of credit to the economy."

The Chancellor is hoping to draw up watertight plans to hit the City's biggest earners in time for Wednesday's pre-Budget report. The new super-tax could be charged directly on British-based investment bankers. There is speculation of a temporary 60 per cent tax rate on earnings over £500,000 or a special tax on high earnings paid in one particular month.