Calls for Northern Ireland First Minister Peter Robinson to step down grew yesterday when the former head of the province's executive David Trimble said he expected his resignation within days.

Mr Trimble said Democratic Unionist Party (DUP) leader Robinson, who insists he will defend his position following disclosures over his family's financial affairs, had lost his authority within the party and the system.

A BBC television programme last week questioned why Mr Robinson did not tell authorities that his wife, also a member of Parliament, had not registered £50,000 (€55,500) received from two people and used to help a man with whom she was having an affair to start a business.

"If he is going to fight to clear his name, the place to do that is from the back benches," the former Ulster Unionist Party leader Trimble, a joint Nobel Peace Prize winner for his part in a 1998 peace deal that ended decades of violence, told the BBC.

"To have a situation where a party leader sees his wife expelled from the party and acquiesces in it, doesn't even persuade the party to give her a decent way out, shows there has been a complete loss of authority."

Citing party sources, the BBC added that Iris Robinson, who last week said she tried to kill herself last year after earlier starting an extramarital affair with the then 19-year-old man, would hasten her exit from Parliament and leave this week.

She had announced her intention to withdraw from public life because of depression late last month.

Separately, Britain's secretary of state to the province said he would have to call a snap assembly election if Robinson were to resign and the power-sharing executive shared between the DUP and Sinn Fein failed to agree on a replacement within a week.