The schemes reward credit card charged travel with units giving discounts on future journeys, or even free trips.
Sir Robin is to send a memorandum questioning the system to all departmental permanent secretaries. The warning that collecting credits through official trips would be improper will rank as part of Questions of Procedure for Ministers, the ministerial behaviour code.
Ministers normally travel at the taxpayers' expense but there is potential for them to benefit from the schemes for personal purchases.
MPs with distant constituencies have been able to use their essential travel, paid for with House of Commons warrants, to clock up miles for future discounts.
Downing Street said there would be 'no objection to air miles being accrued in a way that benefits the taxpayer'.Reuse content