The DUP has said Mrs Robinson is to stand down from public office
The Northern Ireland first minister's wife is receiving "acute psychiatric treatment" as the furore about her private life and finances continues.
A Democratic Unionist Party spokesman said the information on Iris Robinson was being disclosed after speculation about her health and whereabouts.
Peter Robinson is facing growing pressure to resign over the affair.
Meanwhile the Northern Ireland Assembly is due to reconvene amid fears that the power-sharing coalition will collapse.
Former first minister David Trimble has said DUP leader Mr Robinson can "no longer deliver" as first minister.
The DUP spokesman said Mrs Robinson, an MP and member of the Northern Ireland Assembly, was receiving treatment from the Belfast Health Trust.
Reports that she was in a French ski resort were "completely untrue", he added.
Earlier this week, the BBC alleged Mr Robinson did not tell the authorities his wife failed to register £50,000 she obtained from two property developers.
The Spotlight programme said the money was paid to her 19-year-old lover, Kirk McCambley, to help him launch a cafe.
'Clear his name'
Lord Trimble said Mr Robinson had "lost his authority within the party and the system".
"If he is going to fight to clear his name, then the place to do that is from the back benches," said the Ulster Unionist party leader.
David Trimble: "His authority has gone"
Lord Trimble said he expected Mr Robinson to step down within the "next few days".
"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," he said.
BBC Northern Ireland political editor Mark Devenport said DUP politicians had been put under strict orders not to speak to the media.
"Nobody is ringing me and telling me Peter Robinson must be defended and that his situation is impregnable, it is quite the opposite," he said.
"Those that have broken with that instruction have talked about his position being untenable and the real debate being not over his leadership, but over who might succeed him.
"Even if this legal probe that he has ordered clears him of these allegations, on a political level there is huge damage to the Robinson brand."
BBC Ireland correspondent Mark Simpson said it was possible that 2010's first sitting of the assembly could be one of its last.
He said there were major problems at Stormont, the first being the position of the first minister - but also warned that the power-sharing coalition between the DUP and Sinn Fein could break down.
Sinn Fein President Gerry Adams said it was important that the problems surrounding the Robinsons did not detract from the current political impasse over the devolution of policing and justice.
"This is not about the Robinson's private family matters," he said.
"It is about implementing outstanding political agreements that are essential to good government and public confidence."
Earlier on Sunday, a close friend of ex-DUP leader Ian Paisley repeated his view that Mr Robinson's position as Northern Ireland first minister was "untenable".
Free Presbyterian minister David McIlveen stressed that his opinion was not that of Mr Paisley.
Lord Trimble said he expected Mr Robinson to step down soon
His church has also said he was not speaking on their behalf.
"He has a problem with solving his family difficulties and I cannot take the view a person's private life does not affect their public life," he said.
"Judgments that we make in private will undoubtedly influence our judgments in public."
"I do believe that one of the great bonds between a politician and the people is a bond of trust.
"Once that trust is broken, it is very, very difficult to recover that."
On Friday, Mr Robinson said he believed he had not done anything wrong.
However, he added that he would "not be slow" in taking a decision if an investigation found that he should have acted differently.
On Saturday, DUP sources confirmed that Mrs Robinson was stepping down as an MP and MLA and was also leaving the party.
Iris Robinson obtained £50,000 for her lover, Kirk McCambley
She could leave both her posts as early as this week.
Spotlight said Mr Robinson knew about her financial dealings, but did not tell the proper authorities despite being obliged by the ministerial code to act in the public interest at all times.
The financial allegations followed a public admission by Mr Robinson that his wife had attempted suicide after her affair.
Mrs Robinson represents the Strangford constituency in County Down both at Westminster and at the Northern Ireland Assembly.
Last month, she issued a statement saying she was leaving politics due to ill health; however, news that she was stepping down came earlier than expected.
The Robinsons were married in 1970 and have three grown-up children.
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