Two months after Corbyn stole ahead of May in the popularity stakes for the very first time, his lead is slipping as his net favourability rating has sunk to minus 13. May's, on the other hand, has crept up to minus 27.
The proportion of Britons who hold a favourable view of the Labour leader has fallen from 46 per cent in mid-June to 38 per cent now, while the proportion who are similarly appreciative of the Conservative Prime Minister has risen from 29 per cent to 31 per cent.
Yet according to the YouGov survey, the British public still prefer Corbyn to May.
Both of the two main political parties have tracked the success of their leaders. Labour's net favourability has fallen from positive six to minus seven since mid-June, while the Conservatives' has improved from minus 21 to minus 18.
Meanwhile, Vince Cable has come off well from his first favourability survey since taking the reins at the Liberal Democrats in late July.
Although 36 per cent of respondents – more than three times as many than for Corbyn or May – “don't know” whether they have a positive or negative view of Cable, he entered the favourability rankings at the same level as May is currently with a net figure of minus 27.
Cable is running well ahead of his party, which has seen a decline in its popularity from minus 20 in mid-June to minus 33 now.