Former Labour leader lets views on successor Jeremy Corbyn be known to MP Graham Stringer, who criticised his leadership

Ed Miliband’s feelings about Jeremy Corbyn, his successor as Labour leader, have been revealed after he suggested that the party was in direr straits than when he was at the helm.

Miliband had previously kept his opinion about Corbyn close to his chest, but he told Graham Stringer, the Labour MP for Blackley and Broughton: “I bet you didn’t think things would actually get worse.”

Stringer was a vehement critic of Miliband and the former Labour leader told him: “But I won’t be appointing you as chairman of the campaign for me to return as leader”.

Details of the conversation were first published in the Mail on Sunday but were independently verified by the Guardian. His comments, made in the Commons smoking room, emerged at the end of a tough week for Corbyn, in which he has been at odds with some members of his shadow cabinet and many backbench MPs over his opposition to military action against Islamic State.

He also had to contend with criticism of his appointment of Ken Livingstone as co-chair of Labour’s defence review, which intensified when the former mayor of London suggested Labour MP Kevan Jones had mental health problems after questioning his suitability for the post.

Some Labour opponents of the current party leader have sought to blame his predecessor’s reforms to the leadership election for Corbyn’s rise.

Despite Miliband’s comments to Stringer, the latest Ipsos Mori poll suggests Corbyn’s win may have boosted Labour’s popularity. It puts the Conservatives on 37% and Labour on 35% . But this translates to 41% and 34% when adjusted using a method that the pollsters say would have given the most accurate result at this year’s general election.

That compares with the actual result of 38% and 31% at the May election, when excluding Northern Ireland as the poll does. But Labour performed considerably stronger than the final result in opinion polls ahead of the vote.

On Corbyn’s election as leader, Miliband said: “I’ll be offering Jeremy Corbyn my support and I hope people across the party do so too.”