Ed Miliband has been urged to bring back Lord Mandelson as Labour's spin doctor as he faces renewed criticism from within his party.
Prominent backbencher Graham Stringer, a former whip, accused the top of the party of adopting an "almost deafening silence" over the summer.
And he joined other critics in expressing concern that Labour's policies on housing, welfare or education are still unclear.
The intervention comes after shadow health secretary Andy Burnham warned that Labour must "shout louder" and "put its cards on the table" or face defeat in 2015.
It also ignored a plea from a fellow backbencher to end public criticism of the leadership after a series of attacks in recent weeks.
Another comeback? Lord MandelsonJohn Mann wrote on Twitter: "Time for iron discipline amongst Labour MPs. Stop whinging. Message to Ed: give them the boot."
Mr Miliband returns from a two-week holiday in France on Monday and will face calls to get his restive party under control after a difficult couple of months.
Mr Stringer told the BBC there was no challenge likely to his leadership but expressed concern at Labour's decision not to target the coalition over the summer.
"The real worry is the almost deafening silence there has been from the shadow cabinet in a time of the year which is traditionally a ripe time for the opposition to attack the government," he said.
"While the government are on their holidays and thinking about other things, the opposition has always used that as a way to put policies into the public's mind and to have a go at anywhere the government has failed.
"I think the party is genuinely worried about the lack of activity in the shadow cabinet."
He also condemned a "lack of coherence and cogency" on policy.
"It's not quite clear what our policies on welfare are, what our policies on housing are, what our policies on education are," he said.
The MP warned there are a "lot of different views and there is serious concern across the parliamentary party about what our policies should be".
'We must shout louder': Andy BurnhamMr Miliband is thought to be planning a reshuffle before the party conference next month and Mr Stringer suggested Lord Mandelson should return to a key election strategy role.
"There's no doubt that when Peter Mandelson held that kind of position in the past the Labour Party was more cogent and coherent in getting its message across," he said.
"Whether a) he is willing or b) is the right person now, I don't know. But somebody of his abilities needs to be in that position."
Whip Jon Ashworth insisted that Labour was attacking the Government but agreed the party needed to work harder.
He said: "I entirely concede that over the next 20 months as we run up to that 2015 general election, it is now time for us to start coming out with further radical, bold, eye-catching policies."
The autumn conference would be used to set out the "direction of travel", he vowed.