Mr Brown promised in September to "enshrine" the aid figure in law
The Lib Dems have accused Gordon Brown of breaking his "promise to the world's poorest people" in the Queen's Speech.
The prime minister said in September that a commitment of 0.7% of gross national income to overseas aid would "in future become a law".
But in the Queen's Speech, this was presented in a "draft" bill, meaning it is very unlikely to pass through Parliament before the next election.
The Lib Dems said the promise had been effectively "abandoned".
But the government said it was sticking to its pledge and that Labour was the only party which had made a firm commitment to the world's poor.
The Draft International Spending Bill proposes that 0.7% of gross national income is spent on official overseas aid from 2013.
However, with only a maximum of six and a half months until the next election, it is highly unlikely to get the parliamentary time to become law.
Draft bills are issued for detailed consultation, before becoming full bills. Some 13 full bills were proposed in the Queen's Speech with doubts over how many of those might go through Parliament before the election.
In his speech to Labour's annual party conference in September, Mr Brown promised that "what was once an aspiration - 0.7% of national income spent on international development aid, has become with Labour a promise, and will in future become a law".
Following the Queen's Speech, Lib Dem international development spokesman Michael Moore said: "Gordon Brown made a firm commitment to enshrine the 0.7% target for aid spending in statute, but just seven weeks on he has abandoned that promise.
"With a general election only months away, and the Tories' commitment to development issues far from certain, this Queen's Speech is nothing but another broken promise to the world's poorest people."
The publication of a draft bill suggests that a firm commitment may form part of Labour's election manifesto. The Conservatives have pledged to ring-fence the international development budget from spending cuts.
A spokesman for International Development Secretary Douglas Alexander said: "Labour are keeping our promises to the world's poorest people.
"The draft legislation announced today will enshrine in law our commitment to spend 0.7% of national income on international development from 2013. Only Labour has committed to legislate for this promise.
"The Lib Dem leader, Nick Clegg, has instead spent his time arguing there should be no legislation and no Queen's Speech."
Anti-global poverty campaigner Bob Geldof said: "It's good to see the British government taking steps to mitigate the impacts of these predicaments; which is why it is important that this legislation is enacted sooner rather than later."