Jeremy Corbyn has been branded "totally idiotic" by a former top economic adviser after he issued a call for a maximum pay cap for high earners.
The Labour leader said the measure was needed to counter the soaring levels of income inequality between those at the top and the rest of society.
But his comments were dismissed as "totally unworkable" by economists, while business leaders warned the proposal was a "non-starter".
His intervention also appeared to catch senior colleagues by surprise, with one shadow cabinet minister saying he had been expressing a "personal view".
In further comments, Mr Corbyn said he would be prepared to join striking Southern Rail drivers on the picket line while playing down suggestions Labour would curb immigration after Brexit.
The Labour leader raised the idea of a maximum pay cap during a series of broadcast interviews ahead of his first major speech of the year focusing on future relations with the EU.
"If we want to live in a more egalitarian society and fund our public services, we cannot go on creating worse levels of inequality," he told the BBC Radio 4 Today programme .
"I would to like to see a maximum earnings limit, quite honestly, because I think that would be a fairer thing to do.
"We cannot set ourselves up as being a sort of grossly unequal, bargain-basement economy on the shores of Europe."
Mr Corbyn refused to say at what level the cap should be set, although he later told Sky News it would be "somewhat higher" than the £138,000 he earns as an MP and Leader of the Opposition.
He said the salaries paid to some high-earning company executives were "utterly ridiculous" while the pay of top footballers was also "simply ridiculous".
His comments were immediately denounced by Danny Blanchflower, a former adviser to the Labour leader and ex-Bank of England monetary policy committee member, who said it was "totally unworkable".
"Corbyn max wage lunatic idea would generate a huge brain drain as smart people move abroad shows how out of touch he is," he wrote on Twitter. "If I was still an adviser I would have told him it's a totally idiotic unworkable idea."
Richard Murphy, an academic who advised Mr Corbyn during his leadership bid, said the proposal was "incoherent".
"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," he told BBC Radio 4's The World at One.
Oliver Parry, the head of corporate governance at the Institute of Directors, said that while big companies needed to address public concerns about executive pay, a maximum earning cap was a "non-starter".
"Politicians simply do not know the right level of pay for the heads of multinational companies, and no successful economy operates with this level of intervention by government," he said.
"Would the cap also affect entrepreneurs who have built up a successful company, who surely have every right to the rewards?"
Shadow work and pensions secretary Debbie Abrahams sought to play down his comments saying he had made clear he was expressing a "personal view" and that they did not represent party policy.
"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," she told The World at One.
"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."