A planned TV showdown between the Tory leadership candidates has been cancelled because Boris Johnson is refusing to take part.

Sky News invited Mr Johnson and Jeremy Hunt to take part in the event on Tuesday night hosted by Kay Burley.

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The broadcaster has now invited both men to take part in a debate on July 1.

The head-to-head format meant it would not have been possible for Mr Johnson to be replaced by an empty podium on Sky as he was in a Channel 4 debate earlier in the leadership contest.

“Sky News has been planning to hold a debate tomorrow between the two remaining candidates in the Conservative leadership election,” a spokesman for Sky News said.

“Jeremy Hunt has agreed to take part, but Boris Johnson has so far declined the invitation.

“We stand ready to host a debate tomorrow evening if both candidates make themselves available.

Tory leadership contest timetable.(PA Graphics)

“Without both candidates, tomorrow’s debate will not take place.

“But we will reissue our invitation for Mr Hunt and Mr Johnson to debate live on Sky News next Monday, July 1.”

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Mr Hunt used a Times column to urge Mr Johnson to take part in Tuesday’s debate or risk being viewed as a coward.

He said: “Don’t be a coward Boris, man up and show the nation you can cope with the intense scrutiny the most difficult job in the country will involve.”