One of Jeremy Corbyn’s most senior shadow ministers has refused to endorse her leader’s idea of introducing a maximum pay cap, while former expert advisers have publicly branded it "idiotic", "lunatic" and "incoherent".

Shadow work and pensions secretary Debbie Abrahams responded to a question on whether she would support a move to impose a cap on maximum earnings in the UK by saying, "it isn’t a policy".

Former advisers to Mr Corbyn also shot the idea down, with expert David Blanchflower branding it "a totally idiotic unworkable idea" and a "lunatic idea".

Mr Corbyn said on Tuesday that such a cap could help reduce inequality and create a more egalitarian society. But questioned on the policy idea, Ms Abrahams signalled a potential new shadow cabinet rift over the issue.

She told BBC Radio 4's World At One programme: "It isn't a policy. He said in the context of policy development, he said it should be something we looked at and of course we should look at it.

"But everything we do finally say is policy-driven should be based on evidence and I know that Jeremy is committed to that as well."

Mr Blanchflower, a former adviser and ex-Bank of England Monetary Policy Committee member, tweeted: "Corbyn calls for max wage law if I was still an adviser I would have told him it's a totally idiotic unworkable idea.

"Corbyn max wage lunatic idea would generate a huge brain drain as smart people move abroad shows how out of touch he is."

Jeremy Corbyn calls for 'high earnings cap' to reduce inequality

Academic Richard Murphy, who advised Mr Corbyn during his leadership bid, said the proposal was "incoherent".

He said: "It doesn't make any economic sense at all. You cannot impose such a cap.

"Jeremy needs to sit down and get some proper advice. Whoever is advising him now is not giving the right advice or Jeremy isn't simply asking them before making these comments."

The Labour Leader said a "high earnings cap" would help prevent growing inequality, fund public services and prevent a "bargain basement economy".

He said the idea, which he has previously mooted, would bring under control the inflated pay of top executives after research showed UK 'fat cats' earned more than the average £28,000 salary after just four days of 2017.

When YouGov gauged support for a maximum wage of £1m in September 2015, 39 per cent supported it, while 44 per cent opposed.