Updated

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.

He told delegates how he had once been asked what he would do if he found himself in an 'Ashes to Ashes' situation -- a reference to a leading British TV show which sees a modern day policewoman transported back to the Eighties, where she struggles to come to terms with a more 'hands-on' form of policing.

Recalling his response, McDonnell said he would have liked to go back in time to assassinate Baroness Thatcher, former Conservative stalwart and British Prime Minister from 1979 to 1990.

Defending the remark, he told the Guardian afterwards: "It was a joke. And it went down as a joke."

McDonnell, a staunch defender of trade unionism and employment rights, is struggling to get enough votes from his Labour colleagues to feature on the leadership ballot paper.

He needs 33 to stay in the race but has the support of just ten at present. Brothers David and Ed Miliband are the front-runners.