As a dissident republican car bombing campaign returned to Northern Ireland yesterday, seriously injuring a policeman, the First Minister was engulfed in a political and sexual scandal.

In the latest development of the sensational scandal, Mr Robinson said he would fight allegations that he did not report Iris Robinson’s alleged improper financial dealings.

Last night he was said to be resisting calls for his resignation as leader of the Democratic Unionist Party and First Minister, and ordered an official inquiry into his conduct.

“I will be resolutely defending attacks on my character, and contesting any allegations of wrongdoing,” he said.

He claimed his wife had concealed the nature of the donations she obtained along with the illicit affair.

“I had no information,” he said. “Absolutely no information about that, nor of any of the other financial arrangements, which is hardly surprising – if somebody is hiding an affair from you, it’s probably not a surprise they are hiding the other arrangements relating to that affair.”

Mr Robinson’s fall would throw into doubt the survival of the power-sharing agreement between the DUP and Sinn Fein at the Stormont Assembly.

Just two days after an outpouring of sympathy for Peter Robinson over his revelation that his wife had an affair and attempted suicide, the First Minister faced demands to explain his role in her financial dealings.

A BBC Spotlight programme broadcast on Thursday evening questioned why as First Minister he did not inform the authorities about a £50,000 loan to his wife’s teenage lover, Kirk McCambley.

It is claimed Mrs Robinson, who is an MP, an Assembly member and a local authority councillor, broke parliamentary rules to obtain funding for her 19-year-old lover, which she then failed to declare.

Details have emerged of how Mrs Robinson, who has retreated from public life suffering from depression, obtained £50,000 from two property developers. It is alleged she took £5000 of the money for herself and that when her husband found out about the loan and the affair he insisted she pay the money back but did not inform the authorities.

It was also claimed that Mrs Robinson lobbied on behalf of a building scheme in her constituency proposed by one of the developers.

The payments were used to fund Mr McCambley’s refurbishment of a cafe. When the affair ended it is claimed Mrs Robinson demanded the loan back.

The financial allegations effectively finished off the political ceasefire over the affair at Stormont.

Mrs Robinson faced calls from the Alliance Party and Ulster Unionist Party to step down as Strangford MP and Assembly member immediately.

Sinn Fein general secretary Mitchel McLaughlin said Mr Robinson was entitled to defend himself, but if the allegations left him a “hostage” to right-wing elements in the DUP he might have to consider his position.

Adding to the sense of crisis, a Police Service of Northern Ireland officer was seriously injured in a car bomb attack near Randalstown, County Antrim.

Detective Chief Superintendent Williamson said dissident republicans were responsible for the bombing but it was too early to say which group was behind the attack. He described it as an “atrocious act of terrorism carried out by cowardly thugs”.

From sympathy to suspicion in 48 hours

l The emotional public announcement moved many – and signalled a red alert to others. Peter Robinson, the Northern Ireland First Minister and DUP leader, revealed to the nation on Wednesday that his 60-year-old wife Iris, the MP and MLA for Strangford, had tried to kill herself last March after admitting to an affair. He spoke of forgiveness, and of his wife’s fragile mental state.

l One day later, a BBC Northern Ireland documentary was transmitted that alleged financial impropriety on the part of Mrs Robinson – namely, that she secured £50,000 from two wealthy friends to help her then 19-year-old lover Kirk McCambley, now 21, open a cafe on the banks of Belfast’s River Laggan.

l It is claimed Mrs Robinson lobbied on behalf of a building scheme in her constituency proposed by one of the developers, and that she failed to declare an interest at a planning meeting that granted a property lease to the other lender, thus breaking the law.

l According to Mr McCambley, she had two £25,000 cheques made out in his name, but asked him for £5000 back in cash. The affair ended in acrimony after rows about the repayments of the loans.

l If true, Mrs Robinson’s dealings would represent a breach of parliamentary rules and codes. She was said to be unable to comment this week for health reasons.

l Now Mr Robinson’s position is at risk, as he must prove that he was not aware of the situation. Yesterday he vehemently denied accusations that he knew of his wife’s improper financial dealings and failed to alert the relevant watchdogs at either Stormont or Westminster.

l Whatever the eventual outcome, Irisgate has huge implications for the Office of the First and Deputy First Minister. Sir Alistair Graham, the former chair of the committee on standards in public life, said a major investigation into the allegations was called for. However, Sinn Fein general secretary Mitchel McLaughlin made clear that he did not regard Mr Robinson’s possible departure as a devastating blow to the peace process.