An Irish nationalist lawmaker has resigned from Britain's Parliament after sparking outrage by appearing to mock a massacre carried out during Northern Ireland's decades of violence.

Sinn Fein legislator Barry McElduff was shown in a Twitter video with a loaf of Kingsmill brand bread on his head, on the anniversary of the 1976 murder of 10 Protestant workmen by IRA militants in the village of Kingsmill.

McElduff said the video wasn't a reference to the slayings. But he was suspended by Sinn Fein, and quit his seat Monday in Parliament. He apologized for the "deep and unnecessary hurt" his video had caused.

The episode strained Catholic-Protestant relations in Northern Ireland at a delicate time. The power-sharing Belfast administration has been suspended for a year amid a feud between the parties.