Alistair Darling, the former Chancellor, and David Blunkett, the ex-Home Secretary, while they supported the party leader, made it clear it was about time Mr Miliband and his colleagues began the process of telling voters what a potential Labour government would offer in terms of policy.
Mr Miliband, who is expected to start the fightback against his critics at a public question and answer session in Edinburgh on Friday, has been upbraided for his "Zen socialism", which, his detractors complain, is leaving the field open to a pro-active Tory campaign machine.
There has also been criticism of a lack of frontbench profile during the parliamentary recess, with one Labour MP branding it the "summer of silence".
The criticism began with backbencher George Mudie bemoaning Mr Miliband's lacklustre leadership and saying: "I have difficulty knowing what we stand for now."
At the weekend, Lord Prescott, the former Deputy Prime Minister, urged Mr Miliband to sack any slacking member of the frontbench team - a Shadow Cabinet reshuffle is due in the autumn - claiming the party had "got nowhere" since MPs left for the summer recess.
He said: "Radical change is now required to shape up the policy of organisation and delivery alongside a clear set of policies and principles so people know what we stand for."
Even within the Shadow Cabinet itself there was a recognition more needed to be done. Andy Burnham, the Shadow Health Secretary, admitted there was a "need to shout louder" and "put our cards on the table".
Mr Darling, who is leading the campaign against Scottish independence, yesterday stressed no opposition set out its manifesto two years out from an election. However, when it was pointed out that the public did not know what Labour stood for, he replied: "This autumn I know Ed Miliband and Ed Balls will be setting out their stalls."
He added: "Everybody, certainly in my party, is pretty focused on the fact that come this autumn, you are less than two years away, you need to start making it pretty clear to people what would the difference be if, you come to a general election and you vote for a different Government. And that's what we have got to start to do."
Meantime, Mr Blunkett appeared to compare the Labour leader to post-war Premier Clement Attlee, whom, he said, "wasn't the most vibrant" public performer.
He claimed Mr Miliband needed to be "on the ball" at all times and suggested the party must begin setting out policies soon to give voters a clear idea of its vision.
"There is frustration but there is also a great deal of hope. I would accept what's been said over the last few weeks, including the article by John Prescott on Sunday, that we need to work out how to get a higher profile in circumstances where it is very difficult to get a hearing."
Mr Blunkett said Labour must be clearer about its vision, "engage with people in their own lives" and take a "staged approach" to policy, so that by the time the election manifesto was published "people will actually know what we stand for".
A survey found one in three Labour voters thought Mr Miliband should not lead his party into the next general election, while only two out of every 10 voters were satisfied with his performance.
Last autumn, Mr Miliband used the Labour conference to seal the deal with his party; this autumn, it seems clear he has to start a similar exercise with the public, convincing it that Labour is not only an effective opposition but also a potential party of government and that he has what it takes to be Prime Minister.