Ed Miliband has been spared the predicted assault from his own MPs after he told a packed Commons meeting disunity would cost them the next general election just as it had previous polls.

There had been claims the Labour leader was heading for a showdown with his restless backbenchers spooked by his appalling personal poll ratings. But, as is so often the case with such meetings, it didn't happen.

Miliband pointed out the party had remained united over the past four years following its punishing election defeat and insisted he was not about to see that change or allow the chance of election victory next year slip away.

His critics were either absent from the meeting of the parliamentary Labour party or were reluctant to deliver what would have been a very public show of disloyalty.

They are less reluctant in private, however, and the discontent over Miliband's leadership style and demands for him to beef up his offer to the electorate have not gone away but have intensified after the shock Ukip surge in the Heywood by-election.

However, the simple fact a call for unity was seen as necessary spoke volumes.

But no one seriously believes Labour can replace its leader this close to a general election campaign. Not only would it distract the party from the real job of winning the poll but it would risk undermining its current, fragile lead.

However, there are those hard-line critics on the backbenches who believe the party is set to either lose the election or fail to win an outright majority, at which point they would attempt to move against Miliband to get a leader of their choosing in place for 2020.

But this is a small group of the usual suspects, including disaffected Blairites. More worrying for Miliband is the suggestion that the wider parliamentary party continues to have huge doubts about both his personal style and his election strategy.

Party managers deny they are pursuing the "35% strategy" – the minimum result required to win in May – but many backbenchers remain sceptical and believe the clear threat from Ukip means Miliband now needs to do something more robust.

However, he told the meeting: "Normally after an election we show disunity and division. We have had four years of unity. I'm not going to let us, seven months before an election, start lapsing into the bad habits of the past."

He said the party could win in May and insisted: "I am not going to let that opportunity slip away."

And, in a clear message to those dissenters, he declared: "I am going to fight with every fibre of my being to win this election. I expect every person in this room to do the same."