Pete Wishart, the MP for Perth and North Perthshire, used his phone to "tweet" half way through the weekly PMQ joust on Wednesday.
"Thought it would have been a more interesting PMQs first day back. Yawn..!" he wrote.
Moments before, Prime Minister Gordon Brown read out to a hushed chamber the names of the 37 men who had perished in Afghanistan since the last time the House of Commons met, prior to the summer. It took more than two minutes for Brown to read out all the names, among whom was Scottish soldier Sergeant Michael Lockett, whose funeral was held yesterday in Glasgow.
Labour MPs last night claimed Mr Wishart had shown his "disturbing immaturity", but the Nationalist MP issued a statement to claim it was "deeply hurtful and wrong" to argue he had been disrespectful.
He said his comments were in reference to the fact that not one of the three main Labour, Tory or LibDem leaders had chosen to raise the issue of parliamentary expenses.
But Ian Davidson, Labour MP for Glasgow South West, said: "If Pete Wishart finds it boring when the Prime Minister reads out a list of those who fell in Afghanistan during the summer... he displays a disturbing level of immaturity which is out of touch with the people of Scotland. Whatever your political views, the dead deserve our respect. They died serving our country."
A spokeswoman for the SNP said:
"The suggestion that Pete was in any way disrespectful to forces families is deeply hurtful and wrong.
"Pete represents a Black Watch constituency and, along with every MP, sat silently and somberly when the Prime Minister paid tribute to our brave soldiers who lost their lives."