“You can have any rule you like, but you’re supposed to stick to them,” was one City analyst’s reaction to the Treasury’s admission that it may finally change the fiscal framework Gordon Brown introduced with a fanfare when Labour came to power.

As incoming chancellor, Mr Brown staked his reputation for economic competence on meeting two rules: the “golden rule” that the government should only borrow to invest over the economic cycle, and the stipulation that public debt remain at a prudent and stable level, defined as less than 40 per cent of national income.