Owen Smith has totally shot down universal basic income
In practice, universal basic income (UBI) would mean an unprecedented overhaul of the UK's welfare state.
It would involve the means-tested benefits system being replaced by one whereby the government would pay people an unconditional flat-rate payment regardless of their employment status.
John McDonnell, the shadow chancellor and one of Jeremy Corbyn's closest allies, told the Independent last week he believed he could "win the argument" on basic income, despite it not being a current Labour policy. However, Smith said on Monday morning that he would never advocate the policy as Labour leader.
Speaking at a press conference in central London which Business Insider attended, the MP for Pontypridd was asked: "could you see yourself fighting a general election advocating UBI?"
He said: "Honestly, no. I've looked at the arithmetic and I cannot see that this works. I've looked at three or four reports... It's a lovely sounding policy, but I think it's another example of John McDonnell and Jeremy Corbyn, I'm afraid, not being credible on economic policies."
He added: "I think there have been examples during this campaign, where I've sketched out serious ways which we could rebuild Britain, like the £200 billion New Deal I've talked about. John, by contrast, is talking about a £500 billion investment programme funded only through tackling tax avoidance and growing the economy. I don't think that's credible, unfortunately.
"I don't think talking about the universal basic income, no matter how attractive an idea it is, is the answer."
Smith's Monday speech was probably his most blunt attack on Corbyn's leadership yet. His team handed out mock-up Conservative manifestos which listed a host of hardline Tory policies which Smith believes Theresa May will be able to implement without challenge in the coming years due to Corbyn's Labour being an ineffective opposition.
Despite Smith's warnings, Corbyn is set to win the party leadership contest by a margin which could surpass 25%, according to a recent YouGov poll. When BI asked the former shadow work and pensions secretary if he's worried by the poll, he said: "In the GMB vote, real people voting, 26,000 of them voted for me and 17,000 voted for Jeremy. I'm going to take my spear from that as oppose to a poll in the newspapers.
"Polls haven't been very effective recently - real votes tend to trump polls so I'm going to follow the real vote we've had so far which I think indicates I've been absolutely effective in getting that message across."