Northern Ireland MP Iris Robinson resigned from Westminster yesterday after it was revealed last week that she had solicited loans for her 19-year-old lover.

Robinson was expected to stay on as MP for Strangford until May, but a statement from the Treasury confirmed she had left.

It read: “The chancellor of the exchequer has this day appointed Iris Robinson to be Steward and Bailiff of the Three Hundreds of Chiltern.”

MPs are not allowed to resign, so instead they are appointed to an office of the Crown, which the Three Hundreds of Chiltern are reserved for.

Robinson was expelled from the Democratic Unionist Party last week and has also stood down as an Assembly member.

Her husband Peter Robinson, Northern Ireland’s first minister, has stepped aside for six weeks while he fights to clear his name over allegations he knew about the loans but did not report them.

His wife is thought to be receiving psychiatric treatment in a Belfast hospital. She released a statement shortly after Christmas saying she was leaving politics due to mental illness.

A BBC Spotlight programme broadcast last week reported that she had solicited £50,000 from two property developers to help Kirk McCambley, then 19, start a business.

McCambley told the programme he and Robinson, who was 59 at the time, had embarked on an affair.

The contract for McCambley’s business, a cafe called the Lock Keepers Inn, was awarded by Castlereagh council, on which Robinson sits. She did not declare her interest in the business.

The council voted today to hold an inquiry into its decision to award the contract.

The affair was thought to have taken place in the summer of 2008. At the time, Robinson was making a name for herself as a bigot after a string of offensive comments about homosexuality.