Scottish Labour leader Richard Leonard was left “ashen faced” at a proposal for a windfall tax on the North Sea oil industry that has an “85% chance” of being included in the party’s manifesto when it is unveiled today, according to reports.

The Financial Times reported that a plan for an offshore oil industry windfall tax was likely to feature in the document.

The newspaper reported that Mr Leonard’s “face was ashen when this came up” at a meeting of the party’s national executive on Saturday. The Unite branch representing oil workers is the union’s largest in Scotland. Scottish Labour did not comment.

Unveiling the manifesto in Birmingham today, Jeremy Corbyn will accuse the “bankers, billionaires and the establishment” of trying to stop a radical Labour government being elected as he reveals a manifesto for “real change”.

Jeremy Corbyn won the debate, it was claimed. Picture: Stefan Rousseau/PA Wire

The Labour leader will appeal to voters by saying the policies are “fully costed”, with no tax hikes “for 95 per cent of taxpayers”, when he sets out his party’s plans on Thursday.

Mr Corbyn is to tell supporters that the “manifesto of hope” for the 12 December election is full of policies “that the political establishment has blocked for a generation”.

The proposals are expected to include renationalisation plans for key utilities, following Labour’s pledge to take part of BT into public ownership to deliver free full-fibre broadband for all.

It will contain pledges to significantly boost NHS spending, create a £10 minimum wage for all and tackle climate change, creating jobs in a “green industrial revolution”.

The document will also set out Labour’s plan to get a new Brexit deal and put it back to the people in a referendum with the option to remain within six months.

Richard Leonard left ‘ashen faced’ at oil windfall tax within ‘most radical’ Labour manifesto