DAVID VS DAVID Watch the debate In depth: Conservative leadership contest

They will appear together throughout the hour-long, as-live show.

They agreed to take part in principle shortly after the results of the MPs' ballot were announced two weeks ago.

On Friday morning, ballot papers go out to the 300,000 Conservative party members who elect the leader.

"The timing is absolutely critical", said executive editor of the programme Ric Bailey.

This is the weekend when many party members will make up their mind - maybe on the basis of Question Time Ric Bailey, executive editor for the BBC, Question Time

"The ballots go out this weekend and something like 40% of Tory members are expected to vote this weekend."

He added: "I think this is the big event of the Tory leadership battle, in the same way as the party leaders appearing before the general election on Question Time became the central event for that campaign.

"This is the weekend when many party members will make up their mind - maybe on the basis of Question Time."

Around half of the live studio audience will be Conservatives, with the remainder drawn proportionately from the rest of the electorate, providing a broad range of views.

The audience will also be balanced between those who think David Davis or David Cameron would be the better leader of the Conservative party.

Each will stand at a lectern during the programme, as will David Dimbleby who will be in charge of the debate as usual.

BBC One's Question Time is broadcast on Thursdays at 2235 GMT. It can also be watched live and on demand on the Question Time website.