A number of Fianna Fail TDs are warning they won't support the deal to make Leo Varadkar Taoiseach unless Micheal Martin stands down as party leader.

Speaking to the Irish Mail on Sunday, party rebels are threatening not to vote in December, a move that could collapse the government.

The paper reports a number see the 'Rotating Taoiseach' clause in the Programme for Government as their trump card in forcing leadership change.