Chris Leslie labelled it an “okay result” after Jeremy Corbyn’s party secured a higher-than-expected 262 seats and significantly boosted its vote share.
He added that Labour still lost the election, leaving his Nottingham East constituency with a Conservative government “they do not need” and the party with questions about how to convince voters it can move from “protesting about a government into being the government”.
Former minister Mr Leslie said there had been “fantastic results” in some constituencies where Labour had been rumoured to be under threat.
But the Labour MP told BBC Radio 4’s Today programme: “We haven’t won that election.
“We shouldn’t pretend that this is a famous victory. It is good as far as it’s gone but it’s not going to be good enough.
“Five years of Conservative government, I just can’t, I’m afraid, be a cheerleader for that particular outcome because this was an open goal for all of us.
“We should have been getting in there.”
Challenged if Labour could have won under another leader, Mr Leslie said: “I’ve never known a more beatable Prime Minister than Theresa May - brittle, I think very, very wobbly and shaky indeed.”
Pressed again on the question, Mr Leslie said: “I will never apologise for my view, which is yes, you’ve got to of course inspire people, absolutely, and we haven’t done that well enough in the past.
“But you’ve also got to convince them of your credibility that you can actually move from protesting about a government into being the government. Those are the questions we’ve really got to ask ourselves.
“If we fail to ask those questions we may well at the next general election get another 262 - we can pat ourselves on the back about that, of course that’s better, but it’s just not good enough.”