It is relatively easy to work out what that means with a DC scheme: the employer simply pays a proportion of its payroll into it each year.

ECONOMIST: Pensions rules get complex again

Work is currently being carried out to finalise the details of the scheme, including costs and the bikes will be available for hire later this year.

BBC: Boris Bikes scheme for Northampton

The BBC's chief political correspondent, Norman Smith, said Treasury officials were trying to work out a definition of the rules surrounding eligibility for the mortgage guarantee scheme that allowed parents to buy a home for their children but not to buy a holiday home.

BBC: Budget 2013: Row over 'second home subsidy'