Writing in his column in a Sunday newspaper, Lord Prescott said the party had “massively failed” to get its case across and hold the Conservatives to account over the summer.
Lord Prescott urged Mr Miliband to follow the example of former Manchester United boss Sir Alex Ferguson and get rid of under-performing members of his shadow cabinet team.
“If shadow cabinet members aren’t pulling their weight, give them the hairdryer treatment and kick ‘em out,” he wrote. “Time is running out. We can still turn it around and win in the second half. But we need the very best team, week in, week out.”
Latest polling yesterday found Mr Miliband has suffered a slump in his ratings after a summer of sniping over his leadership from within his ranks.
A ComRes poll showed 22 per cent thought he was doing a good job compared to 50 per cent who did not.
It gave him an overall personal approval rating of minus 28 – a 17 point fall since May – representing his worst showing in a ComRes poll.
The findings put him near level-pegging with David Cameron on minus 27, a drop of two points. There was more criticism for Mr Miliband from his one-time guru, the academic Lord Glasman, who said the Labour leader needed to show he was a “grown-up politician” able to lead the country.
“At the very time when Labour should be showing the way ahead, it gives the impression of not knowing which way to turn,” he said.
“When the Labour battle bus should be revving up, it is parked in a lay-by of introspection.
“It is time for Ed Miliband to show he is a grown-up politician big enough to lead this country.”
Overall, the position of the main parties shows little change, with Labour up one point since last month on 37 per cent and the Conservatives unchanged on 28 per cent.
The UK Independence Party continues to enjoy strong support with 19 per cent – a one point rise – while the Liberal Democrats trail a distant fourth on 8 per cent.
Shadow energy secretary Caroline Flint acknowledged that Labour needed to “redouble our efforts to win the confidence of the public”, but insisted the Mr Miliband’s poor poll ratings could be overcome.
“Individual popularity poll ratings are always given prominence, but the truth is that, when it comes to the election, that’s not always a significant factor,” she said.
“Think back to Labour leaders in the past who were popular but couldn’t win elections. [Tory] Margaret Thatcher was unpopular but won elections. Sometimes these things are overplayed.”
Meanwhile Labour officials confirmed that they were considering a cut in the voting age in England and Wales from 18 to 16 as part of their manifesto.
Shadow justice secretary Sadiq Khan said the change should be combined with improved citizenship education.
The franchise has been extended in Scotland to allow this age group to vote in the referendum next year.