Labour should avoid routinely opposing government spending cuts, shadow defence secretary Jim Murphy has said.
He told the Guardian his party needs to achieve "genuine credibility" on the economy in order to build popularity.
It is the second time this week that a senior Labour figure has cast doubt on the party's economic strategy, after criticism by ex-adviser Lord Glasman.
Labour is in the middle of wide-ranging policy review which could report some time later this year.
In the newspaper interview, Mr Murphy suggests Labour can only have the credibility to oppose some of the government's spending cuts if it is seen to be more willing to agree to others.
He says there are £5bn of defence cuts he would agree to.
The shadow defence secretary's comments come just two days after Lord Glasman, who has advised the party leader in the past, said Mr Miliband seems to have "no strategy and little energy".
He told the New Statesman he "backed" Mr Miliband as opposition leader but he needed to change his approach if he was to "break through".
Lord Glasman later denied that his comments were meant as an attack on Mr Miliband and attempted to play down his role behind the scenes.
BBC political correspondent Alan Soady reports: "Labour sources say Jim Murphy's intervention is in no way intended as a criticism of Ed Miliband and that it builds on remarks by the shadow chancellor, Ed Balls, that Labour needs to be more up-front about spending cuts."