A British politician sparked controversy Monday when he made a quip about going back in time to assassinate the former Prime Minister, Margaret Thatcher, the Guardian reported.

John McDonnell, a staunch left-winger and contender for the Labour party leadership race, later insisted the remark was a joke.

The Member of Parliament made the comment as he spoke to trade unionists in Southport in northwest England.

McDonnell described how he had clashed with Thatcher while working at the National Union of Miners and the Greater London council in the 1980s.