The wife of Northern Ireland's First Minister Peter Robinson has been found guilty of a serious breach of a politicians' code of conduct over her business dealings with a teenage lover.

Former MP Iris Robinson accepted £50,000 from two property developers and passed it on to 19-year-old Kirk McCambley to set up a business in Belfast in summer 2008, a Stormont report said. Mr McCambley later paid her £5,000.

The Robinsons were once the power couple of Northern Ireland politics, as MPs for the neighbouring constituencies of East Belfast and Strangford and senior figures in the Democratic Unionist Party (DUP).

But when news of the affair broke in 2010, Mrs Robinson withdrew from public life following bouts of depression, and her husband temporarily stood aside at the head of the power-sharing ministerial executive while the peace process was ­destabilised and former prime minister Gordon Brown called crunch talks.

Today's report by Assembly Standards Commissioner Douglas Bain exonerated Mr Robinson, but found Mrs Robinson in breach of the code.

Mr Bain said: "Although there is no evidence that any of the three payments was in fact connected with her role as an MLA (Member of the Legislative Assembly), they would assuredly have been perceived, by members of the public who became aware of them, as likely to influence her actions as an MLA. The fact that she failed to register them itself adds weight to the perception of their improper nature.

"In these circumstances she had a clear duty to register the payments. She failed in that duty. Her failure was a serious breach of the 1999 Code of Conduct."

Mr Robinson, who leads the DUP, was cleared over separate claims made in a BBC Spotlight programme that he broke the ministerial code of conduct.

In January 2010, Mrs Robinson's dealings with her teenage lover were revealed, including that she obtaining £50,000 to help Mr McCambley secure a public tender for a busy south Belfast cafe, the Lock Keeper's Inn.

That business on the banks of the River Lagan was in the district of Castlereagh Council, of which Mrs Robinson was a member.

The disclosure of the relationship and associated business ­dealings caused shockwaves in Northern Ireland.

Mrs Robinson first met Mr McCambley, 19, when he was working in his father's butcher's shop, the standards commissioner's report said. The short-lived fling lasted from mid-summer 2008 to the end of the year.

She and her husband had been friends of late developer Fred Fraser and fellow property tycoon Ken Campbell for more than 30 years. Both were well-known, particularly in North Down, which is close to the couple's constituencies. They agreed to pay her £25,000 each, which she passed on to Mr McCambley to support his new business.

Mr Campbell was seeking and received the Strangford MP's support for a planning permission application at the time Mrs Robinson asked him about the money, an interest-free unconditional loan of £25,000, the report said.

Mr McCambley subsequently paid £5,000 to Mrs Robinson, to be used for charitable purposes, the report said.

Spotlight alleged Mr Robinson had contravened the ministerial code of conduct by failing to tell the House of Commons about the money, and failed to tell the proper authorities his wife had broken the law by failing to declare her receipt of money from the developers.

The commissioner's report said: "Mr Robinson first learned of the £5,000 paid to his wife by Kirk McCambley from the Spotlight broadcast in January 2010. I am satisfied that none of the allegations made in that programme against Mr Peter Robinson could, even if established as true, constitute a breach of either the 1999 or the 2009 code of conduct."

The devolved assembly's Standards and Privileges Committee of public representatives accepted the findings. Chairman Allister Ross denied the report was a whitewash.

He said: "The investigation was carried out independently and has made a number of findings. I do not think anybody could call it a whitewash at all."