Hard to levy windfall tax

There are huge practical difficulties in imposing a one-off windfall tax on banks operating in Britain, a source familiar with the matter told Reuters on Sunday.

"There are really big difficulties doing anything like this" the source said. "You wouldn't want to do anything that eroded banks' capital."

There has been rising speculation that Chancellor Alistair Darling will announce some kind of new levy on banks in his pre-budget report on Wednesday.

A government source told Reuters on Friday that a windfall tax was one option but there were problems around its implementation.

The BBC reported on Sunday that the Treasury was considering an annual 1 billion pound levy over three years.