20/05/2016 13:04 BST | Updated 20/05/2016 13:40 BST

Labour's Tom Watson Says 'Selfish' Boris Johnson Has 'Hijacked' EU Referendum For 'Political Ambition'

'Boris Johnson has decided to use the EU vote to further his own career and force his way into No 10.'

Stefan Rousseau/PA Wire

Labour's Deputy Leader Tom Watson has launched a brutal attack on 'Brexit' cheerleader-in-chief Boris Johnson, claiming the Tory MP has "hijacked" the referendum for "political ambition".

Writing for The Huffington Post UK, Watson dismissed the idea Johnson's wish to leave the European Union is a "sincerely held view" and is instead a "political calculation" to "increase his chances of becoming Prime Minister".

Johnson reportedly wrote two columns for The Telegraph when announcing his intention to leave - one for Leave and one for Remain.

Watson's attack is notable for Labour ramping up the rhetoric against him against the likelihood of Johnson being the Tory leader at the next 2020 election.

Jonathan Brady/PA Wire
Labour party deputy leader Tom Watson

In one striking extract, he says:

"This referendum has been hijacked by one man who never fails to place political ambition before principle.

"Boris Johnson has decided to use the EU vote to further his own career and force his way into No 10 - regardless of the cost to the country and seemingly his own party.

"It is cynical. It is short-sighted.  It is selfish. And I believe the British electorate will see through it."

Watson details how Johnson two years ago wrote: "Leaving the EU will be globally interpreted as a narrow, xenophobic, backward-looking thing to do."

"Now he is the cheerleader for the Leave campaign," Watson adds.

Even before his announcement at an impromptu press conference, some made clear they thought he was not a true believer - including Tory MP Nicholas Soames, the grandson of Winston Churchill.

David Cameron has said he will stand down before the next election and many feel whether the UK votes to Leave or Remain on June 23 than a Tory backing 'Brexit' is in pole position.

In 2012, Johnson signalled he was more aligned to underlining the benefits of EU membership: “If we get to this campaign, I would be well up for trying to make the positive case for some of the good things that have come from the single market.”