The Labour leader claimed five million people in work could not make ends meet and promised that Labour would set a statutory minimum wage target, linked to average earnings.
At present, the adult rate is due to rise in October from £6.31 an hour to £6.50 an hour.
While he did not reveal a precise figure, Mr Miliband said he would announce one nearer the 2015 General Election. One suggestion has been to raise the minimum wage to 60% of median earnings to around £7.14 an hour.
But Katja Hall, CBI Deputy Director-General, warned him against turning the minimum wage into a political auction.
"The national minimum wage has been a success in raising wages for the lowest paid because it's been left to the Low Pay Commission, not politicians, to set the rate," she declared.
Adam Marshal at the British Chambers of Commerce said most firms would support a higher minimum wage but only on the basis of careful evidence and warned that politicking by parties could lead to "unaffordable promises that will cost jobs and growth".
Simon Walker, Director General of the Institute of Directors, said Labour was right to push for workers to see the benefits of economic growth but also warned: "The minimum wage must not become the subject of a political competition to see who can offer the most, irrespective of what the economy and employers can afford."