A “crisis” for Theresa May after Jo Johnson quit the Cabinet over her Brexit plan and demanded a second referendum tops most of the Saturday papers.

Boris Johnson’s brother issued an uncompromising assessment of the Prime Minister’s attempt to pull together a deal with EU, warning the country faced a choice between “vassalage” or the “chaos” from crashing out.

Remain-backing Jo Johnson said he agreed with his Brexiteer sibling, who quit as foreign secretary over the plans in July, and branded Mrs May’s deal being hammered out with Brussels a “terrible mistake”, the Daily Mail reports.

The Times picks out another of his parting shots, in which he said presenting the nation with a choice between her deal or no-deal is “a failure of British statecraft on a scale unseen since the Suez crisis”.

The Guardian quotes from the blog post extensively on its front page, saying it has plunged the PM’s hopes of getting her deal through Parliament into doubt.

The Daily Telegraph also says his resignation is a “major blow” to the PM’s hopes of getting MPs’ backing for the plan, while she must now face the Johnson brothers’ “combined heft”.

However, as well as her Cabinet loss, the PM is facing further woes in the form of DUP warnings that the plan would “betray” Northern Ireland, the Financial Times reports.

And the Daily Express says Mr Johnson has sparked fears the PM could face further ministerial resignations in the coming days.

In other news, the Daily Mirror and Daily Star lead with Strictly Come Dancing’s Danny John-Jules.

And a “super mum” who has given birth to her 21st baby after a 12-minute labour leads The Sun.