An Ulster Unionist Party MP said he hurled two Tricolours into the River Thames after he was "insulted" by their presence.
Mr Ken Maginnis, MP for Fermanagh and South Tryone and the party's security spokesman, said the flags were on display in the Strangers' Cafeteria at the House Of Commons for St Patrick's Day.
"They have nothing to do with St Patrick", he said. "In Northern Ireland and Great Britain the Tricolour is a flag of convenience for the IRA. If they had put up a St Patrick's flag, that would have been a very different matter.
"I received complaints about their presence, so I went down, and handed them to a member of the staff insisting they should be removed. Ten minutes later I heard they had been replaced. So I went down again and disposed of them in the most effective way I could: I dumped them in the Thames," he said yesterday. "I and a lot of other people were insulted by their presence."