The former London mayor, now a key campaigner in the push for Britain to leave the EU, was quoted in an interview published by this week's Sunday Times as confirming that his hair was coloured.
"This is the real thing," Johnson reportedly said. "It's all natural". But when asked whether he dyed it, the 51-year-old added: "Yes".
But the paper's political editor Tim Shipman, who conducted the interview, wrote on Twitter after the comments appeared Sunday that Johnson had contacted him to insist he had "never" used hair dye.
"Boris Johnson has just called to say he thought I was joking about hair dye and that he was joking too about using it!" Shipman wrote.
Johnson's shaggy, unruly hair has helped make him one of Britain's most recognisable and popular politicians, along with his bumbling manner and witty soundbites.
The Conservative lawmaker split with Prime Minister David Cameron by announcing in February that he would campaign for Britain to leave the EU in the June 23 referendum.
He is one of the favourites to succeed Cameron if the premier steps down following the vote, which looks like a close fight between "Leave" and "Remain".
A Sunday Times/YouGov poll this week found that 20 per cent of those surveyed wanted Johnson to take over from Cameron, well ahead of his rivals.
That is despite Johnson once insisting that his chances of becoming prime minister were only slightly better than those of him "being reincarnated as an olive".
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