A key architect of Zac Goldsmith's "dog whistle" and "racist" London mayoral campaign in 2016 has been recruited by Boris Johnson to help run his final push for No 10.

Mark Fullbrook, a man behind the Conservatives' failed bid in the capital, will be the campaign chief executive for Mr Johnson who maintains his status as the frontrunner in the leadership contest.

It comes as Iain Duncan Smith, the former Conservative leader and leading member of the the hardline group of Tory Brexiteers, was appointed as Mr Johnson's campaign chairman.

Mr Fullbrook – a partner of the election strategist Sir Lynton Crosby – has been targeted for managing the transition between the contest moving from Tory MPs to members.

He also worked alongside Mr Johnson for his successful bid for London mayor and his firm was hired by Theresa May to run her disastrous snap general election in 2017.

But the political strategist was also campaign director in the Tories' unsuccessful battle against Sadiq Khan over three years ago, which was condemned as Islamophobic.

In response to the announcement, a Labour source told The Independent: "Mark Fullbrook was a key architect of Zac Goldsmith's vile dog-whistle campaign in the 2016 mayoral election - widely condemned as the most racist campaign in modern British history."

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Baroness Warsi, the former Conservative co-chair, also criticised Mr Goldsmith's campaign at the time, after an article he wrote attacking Mr Khan was illustrated with an image of a bus destroyed in the 2005 7/7 terrorist attacks in London.

Once the Tory MP was defeated, she added the "appalling dog whistle campaign" lost the Tories the election and "our reputation and credibility on issues of race and religion".

Labour's Yvette Cooper also criticised the campaign of "becoming a full-blown racist scream" - a claim rejected by Mr Goldsmith as "absurd" at the time, as he insisted his campaign had been "overwhelmingly positive".

Asked by The Independent in 2016 after losing the race whether he regretted the tactics used, Mr Goldsmith replied: "I regret losing the race because I had an exciting plan I'd put a lot of work into developing a programme for London. My manifesto was brilliant – I didn't write it myself which is what allows me to say that."