Ed Miliband is facing fresh criticisms over his leadership after one of his MPs accused the Labour hierarchy of an "almost deafening silence" since parliament went into recess for the summer.

Former whip Graham Stringer has joined the voices from within the party arguing that it needs to set out its policies more effectively. Amid concerns over a lack of dynamism in the shadow cabinet, Miliband is set to reshuffle his frontbench in September before Labour's party conference.

Echoing comments by fellow Labour backbencher George Mudie earlier this month, Stringer told BBC Radio 4's World at One he was not clear what the party's housing, welfare or education policies were.

"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," said Stringer.

"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."

David Cameron and Nick Clegg have made numerous media appearances over the summer in a bid to set the news agenda.

Accepting that there was no need to set out Labour's manifesto for the next election now, Stringer nevertheless argued that the party and public had a right to expect "clear and coherent policies". He called the unity that had been portrayed within the parliamentary party "a bit of a mirage" amid serious concern about what Labour's policies should be.

On Friday, the shadow health secretary, Andy Burnham, became the first frontbench spokesman to publicly call for more action from Labour. In an interview with the Guardian, he said: "I think there's definitely a need to shout louder, and speak in a way that captures how people are feeling and thinking. There's definitely a need to put our cards on the table."

Stringer suggested the reshuffle, prompted by the unexpected resignation of Tom Watson as the party's general election co-ordinator in the wake of the vote-fixing scandal in Falkirk was an opportunity to bring in a heavyweight figure such as Lord Mandelson, who he said could replace Watson. "Somebody of his abilities needs to be in that position," said Stringer.

Responding to his comments, Labour whip Jon Ashworth said Labour had identified policies but could do more to communicate them.

"On housing, we have talked about the fact that we want to build more housing. On welfare, we want to introduce a job scheme to get people back to work," he said. "Do we need to work harder to get our messages across? Of course we do." He added: "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, eyecatching policies."

Labour has dropped three points in the last two weeks leaving them with a lead of just 7% over the Conservatives, according to a new Opinium/Observer poll.

Labour stands on 36% of the vote compared with the Conservatives' 29%. Both Ukip and the Liberal Democrats have enjoyed single point gains, rising to 17% and 9% respectively.

The new poll suggests that the prime minister's approval rating has accordingly improved, with 34% approving of him compared to 33% two weeks ago.

It also found that 49% disapprove of Cameron, down from 50%, giving him a net rating of -15%, his best rating since January.

Miliband, meanwhile, has suffered from a decrease in the proportion of people who approve of him – from 22% to 21%. The proportion who disapprove has gone up from 44% to 47%.