A police investigation has been opened into claims that former Northern Ireland MP Iris Robinson acted illegally when she procured loans for her teenage lover’s business.

Robinson was alleged to have solicited £25,000 each from the two property developers, Kenny Campbell and Fred Fraser, to help Kirk McCambley, then aged 19, set up a cafe in Belfast.

It was claimed that she kept £5,000 for herself and failed to declare the loan or her interest when the local council, on which she sat, awarded a contract to McCambley.

She was also alleged to have lobbied for three planning applications on behalf of Campbell and Fraser.

The allegations were aired in a BBC Spotlight programme and a police statement given to the broadcaster said the investigation would “seek to establish whether any criminal offence has been committed by Iris Robinson. . . and by any other person referred to in the programme”.

The statement added: “The police service is aware of the substantial public interest in this investigation. The police remit is to investigate potential criminality, nothing else. Police will be making no further comment on the investigation at this time.”

This is not the first time Robinson has faced a police investigation. Last year, she was investigated by police for homophobic comments she made in 2008.

Robinson had compared homosexuality to paedophilia, called gays an “abomination” and suggested they could be cured. Last March the Public Prosecution Service decided she had not committed an offence and the case was dropped.

Robinson has since quit as MP for Strangford and a member of the Assembly. She is said to be undergoing psychiatric treatment in Belfast.

Her husband Peter Robinson, who is Ireland’s first minister, was accused of knowing about the loan but failing to report it.

He denies any wrongdoing and has temporarily stepped aside from his positon in an attempt to clear his name.