Opposition parties have joined forces to make the Welsh Assembly Government re-draft its 2006 budget.
Two independents - including former Labour AM Peter Law - voted with the three main opposition parties to ensure Labour has to revise its spending plan.
Opposition AMs want the re-drafted budget to put more cash into education, council tax and rail services.
Labour said the opposition's demands on its £13.8bn budget amounted to an "uncosted wish list".
The main opposition parties, Plaid Cymru, the Conservatives and the Liberal Democrats were joined by John Marek, of Forward Wales, and Blaenau Gwent Independent Peter Law for the vote.
They said they wanted the government to provide more money to assist council taxpayers who had suffered as a result of rebanding.
The final draft of the budget will have to be agreed by December
They also said they wanted more money for higher education, a small schools fund and Welsh rail services.
After setting out the five areas they wanted money spent on, they used their collective voting power to instruct finance minister Sue Essex to come back with a new document.
Ms Essex said she knew opposition AMs had the power to defeat the draft budget, but she warned them that they were risking carefully calculated spending plans.
She pleaded with opposition AMs not to "vote us down" simply because they could.
'Depth of anger'
She told the assembly: "This is not about doing things that you have got the power to do just because you have the power. It's about doing the right things."
During the debate, Huw Lewis, Labour AM for Merthyr Tydfil and Rhymney, said: "We have produced a serious budget which will increase investment in the areas that need it most. The opposition proposals would mean a cut to vital front-line services.
"The people of Wales would expect a serious alternative budget from parties aspiring to form a government. Instead we received an uncosted wish list."
Plaid Cymru assembly group leader Ieuan Wyn Jones said: "What I think is absolutely crucial here is that this government understands the depth of anger there is, the length and breadth of Wales, about council tax bills.
"And I belive that it is crucial that the finance minister understands that and that it is included in the budget."
Liberal Democrat group leader Mike German said: "Fundamentally it is [the] national assembly's budget we're talking about, not Labour's budget."
Labour has been in a minority in the assembly since Blaenau Gwent AM Peter Law became an independent earlier this year. The opposition now holds 31 of the 60 seats.
It is understood that each of the party leaders will hold private talks with the first minister to reach a deal for the final draft of the budget to be agreed by December.