This follows a recommendation by the Competition Commission. The supermarket ombudsman's new Groceries Supply Code Of Practice (GSCOP) will come into force from 4 February.
Consumer affairs minister Kevin Brennan said the powers of ombudsman and the details of the enforcement code would be finalised after a consultation next month.
The ombudsman has been championed by the National Farmers' Union which says shoppers pay up to £1.70 for two litres of milk for which the farmer receives less than 50p.
'War on Want', a London-based anti-poverty charity organisation, says a supermarket ombudsman would also help poorly paid workers in the developing world.
However, the British Retail Consortium said the new plan calls for unnecessary and costly new bureaucracy which would raise prices for consumers.