Tory MPs have expressed fears that Boris Johnson will get such a commanding lead in the leadership race that some of his supporters will vote tactically in the final parliamentary round to ensure the “weaker challenger” gets through to the head-to-head contest.

With three more voting rounds planned next week, the former Foreign Secretary already has a huge lead, winning 114 votes out of 313 in the first round; 71 ahead of his nearest rival Jeremy Hunt and 77 votes ahead of Michael Gove.

With four of the original 10 candidates no longer in the race – Matt Hancock withdrew on Friday after securing just 20 votes in the first round – 50 MPs will have to choose a new preference. But it is thought some MPs who have voted for other candidates will swing strongly behind Mr Johnson as the clear frontrunner giving him an even greater lead.

READ MORE: Boris in pole position to be next PM

One senior party source told The Herald: “Boris’s supporters could begin to vote tactically to ensure whoever they regard as the weaker challenger ends up in the final two with him. They could lend their votes to someone else.”

Asked about the prospect, one Conservative MP said: “Yes, I am concerned. Gove and Boris would be a good contest and a real challenge. We want any leader to be put through their paces.”

A second Tory MP said such tactical voting was “not an impossibility,” noting: “Michael Gove is the opponent Boris least wants to see sharing a hustings platform with him. He has a justified reputation for mastering detail, for articulating policy ideas, for getting his points across in debate and under studio lights.”

Another Conservative backbencher noted: “I’ve been told that this is the kind of thing that pretty much always happened in the past. As one colleague put it: ‘You are dealing with the most duplicitous electorate.’”

Mr Johnson told the BBC he would not be taking part in Channel Four’s live TV debate on Sunday evening because he believed, with six candidates, it would be too “cacophonous”. However, he confirmed he would participate in the BBC debate on Tuesday night.

He said: “The public have had quite a lot of blue-on-blue action frankly over the last three years. We don't necessarily need a lot more of that.

“So, the best solution would be to have a debate on what we all have to offer the country…and the best time to do that would be after the second ballot on Tuesday and the best forum is the proposed BBC debate.”

READ MORE: Boris Johnson 'is driving Britain towards a Brexit cliff-edge'

Eaarlier, Mr Johnson was criticised for a lack of media appearances, with his rival, Jeremy Hunt, accusing him of hiding from the media and preventing a wider debate within the party.

"We can only have that debate if our front-runner…is a little bit braver in terms of getting out into the media and engaging in…the TV debates," declared the Foreign Secretary.

On Monday, the six candidates will face another round of hustings before MPs organised by the 1922 backbench committee but they will also be grilled by Westminster journalists at a separate event. However, one absentee at the latter hustings will be Mr Johnson. His camp said he had to prepare for Tuesday’s TV debate.

In his BBC interview, the former London Mayor:

*claimed it was "perfectly realistic" to renegotiate the Withdrawal Agreement to allow Britain to leave the European Union by October 31;

*argued the Irish backstop could be dropped by using “maximum facilitation techniques”;

*said he would “continue to be the kind of politician I have been for a very long time” despite people trying to trip him up or expose a gaffe;

*stressed he did not want a no-deal outcome but a “smooth and orderly managed Brexit” yet to achieve the latter, Britain had to convince Brussels it was preparing for the former and

*denied using cocaine since a "single inconclusive event" aged 19 more than 30 years ago.

Meanwhile, Tory HQ announced the dates for the 16 hustings before the party grassroots. They will begin on June 22 in the West Midlands and end on July 17 in London. The Scottish event will be on Friday July 5, probably in Perth.