In a possible blow to hopes the scheme will be replicated north of the Border, Chief Secretary to the Treasury Danny Alexander said Scotland would receive a share of extra Department for Education spending.
But he refused to say how much the Scottish Government would receive, saying full details would be revealed in Chancellor George Osborne's autumn statement.
The Scottish Government has come under renewed pressure to provide free lunches for pupils aged five to seven since Nick Clegg announced the service would start in English schools next year.
UK Government sources suggested Scotland would receive £60 million as its share of the £600m initiative.
Mr Alexander's comments came in reply to letters from Scottish Finance Secretary John Swinney seeking clarification on the proposals.
Mr Swinney said: "I only hope they have not misled people and that they do deliver the increase in the overall budget which they trumpeted at their conference." He added that last year's autumn statement removed £100m previously promised for public service budgets in Scotland.
At present, one in four Scots pupils qualifies for free meals.