Conservative MP Nigel Mills has issued an apology for playing popular mobile puzzle game Candy Crush Saga during a Commons committee hearing.
Pictures were published in the Sun newspaper of the MP playing the game on his tablet during a Work and Pensions Committee session on pensions.
Mr Mills, a committee member, had initially admitted playing and told the newspaper he would try not do it again.
But he later apologised "unreservedly" for his behaviour.
The MP for Amber Valley was said to have played Candy Crush Saga over a period of two-and-a-half hours.
It was during the committee's evidence session on pension reforms, which took evidence from representatives of the pensions and insurance industries ahead of the Autumn Statement.
In a statement on Monday afternoon, the MP for Amber Valley said: "I apologise unreservedly for my behaviour at the committee meeting and realise it fell short of what is expected of a member of parliament. I guarantee it will not happen again."
Mr Mills had initially told the paper that he "probably had a game or two" but said he was "fully engaged" in the hearing and would "try not to do it" again.
'It was boring!'
The House of Commons authorities have now launched an investigation because the photographs in the Sun of Mr Mills playing Candy Crush were a breach of parliamentary rules.
A Commons spokesman said the Serjeant at Arms' probe could lead to the person who took them being banned from the Houses of Parliament.
Prime Minister David Cameron said Mr Mills was a "very hard-working" MP and would be "embarrassed" by what had happened.
But Conservative MP Sir Edward Leigh had some sympathy for his party colleague, recalling his own boredom when he used to chair a Commons committee.
"I would say get a life. I survived nine years as chairman of the Public Accounts Committee and I just about managed not to go to sleep and not to play computer games but my god, it was boring! So if Nigel has to keep himself awake by playing computer games, good on him," he said.
TaxPayers' Alliance spokesman John O'Connell criticised the Commons investigation as "pointless" and a "nonsense".
He said the issue was not who took the photos of Mr Mills but why he was playing the game in the first place, "and why Parliament insists on these outdated filming regulations for what is, lest we forget, a public meeting".
Candy Crush was the top downloaded free mobile app of 2013. Users must swipe the screen to match grids of brightly coloured sweets to score points and pass different levels.
Mr Mills, 40, was first elected as an MP in 2010 and was a borough councillor before that. He has a classics degree from Newcastle University and is a qualified chartered accountant, having worked as a tax adviser before entering parliament.
His political interests include employment, crime, anti-social behaviour, education and taxation.