"Ed Balls is doing a great job as Shadow Chancellor," the Labour leader told ITV News.
"Three years ago, Ed Balls stood out against what most people thought and said 'I don't think this austerity is going to work'. What you find now, nearly three years on, is a lot more people agree with him than agreed with him at the time. Getting those judgments right is incredibly important."
In the survey, carried out by ComRes for the broadcaster, only 17% said they trusted Mr Balls to "see the country through the current economic situation" compared with 21% for his Tory counterpart.
Clear majorities - 57% and 54% - said they did not have faith in either politician to do so.
More than a quarter (27%) said they would be more likely to trust Labour's economic policy if someone else was leading it - though 35% disagreed and 38% said they didn't know.
There was a starker gap between those expressing confidence in David Cameron and Mr Miliband - with the Prime Minister trusted by 33% and not trusted by 49% compared with 23% and 53% for the Opposition leader.
Mr Miliband also said he would maintain his opposition to a 1% cap on annual rises in working age benefits - a real-terms cut - despite criticism that voters back the Government's welfare squeeze.
"I'm doing what I believe and you know what's really important - you've got to do what you believe. The one thing people want from politicians today is for them to stand up for what they believe in.
"On the question of the 1% cap, 60% of the people affected by that are in work. They're the supposed strivers.
"I am not going to divide our society into saying all of the people looking for work are somehow skivers. Yes, there are a minority who should be working and aren't...but I'm not going to play the George Osborne politics because it's the wrong thing to do."
ComRes interviewed 2,019 British adults online between 19-21 April.