The former Shadow Energy Secretary played down calls for Mr Corbyn to stand down but warned he needed to demonstrate the party was making “a hell of a lot more progress”.
She backed new London mayor Sadiq Khan’s call for Labour to “reach out beyond the big cities”, adding the party must also “reach out to those people who voted Conservative”.
The former Europe Minister described last week’s local election results as the “worst resuilt for an opposition party after a general election for 30 years.”
Ms Flint said: “It doesn’t take away from the hard work on the ground by Labour councillors, parliamentary candidates and members in these elections but we need to be making far more inroads to be within an opportunity to win in 2020.
“That’s the challenge for Jeremy. He deserves the right to lead, he won the [leadership] election but he has to show what has he learnt from these elections, will he talk to people like Sadiq Khan to think about how we broaden our appeal so that we can be in a very position come 2020.”
Ms Flint added: “We’re having a debate about what is the Labour Party for and we have to decide are we a party of protest or are we a mainstream democratic socialist party that is competitively challenging for government?”
Dearne Valley MP John Healey said: “Every new party leader has to prove himself. It’s only eight months since he was elected.
“But for my money, that mandate to lead must also be a mission to win and it’s that single-minded job now, our sole purpose, must be to win back a hearing and then the support of the millions of people in Scotland and across swathes of middle and southern England and Wales that deserted us and weren’t convinced by us in 2015.”