A Twitter page is displayed on a laptop computer in Los Angeles October 13, 2009.[Agencies]

OTTAWA - A Canadian member of Parliament learned the hard way on Tuesday that insulting a rival legislator by Twitter is not a good idea, especially if you're sitting around the same table at the time.

Michelle Simson of the Liberals, unhappy at the behavior of Conservative parliamentarian Dean Del Mastro during a committee meeting, sent a Twitter message saying "Del Mastro should grow up (not out)".

Del Mastro, who is not slim, stood up in the House of Commons in front of hundreds of legislators to demand Simson say she was sorry.

"I apologize that I'm not perfect and perhaps my stature doesn't meet the criteria that some members of the House might set but I have actually battled that problem since birth," he said.

Simson then apologized publicly, saying she had been wrong.