The Senate has rejected the Abbott government’s legislation to abolish the carbon tax – a core election promise of Prime Minister Tony Abbott.

After months of debate Labor and the Greens combined to vote against the repeal laws 33 votes to 29 today.

Labor and the Australian Greens used their combined numbers to quash the legislative bundle, prompting cries of “shame” from government senators.

Labor, which introduced the carbon pricing scheme in 2012, says the Coalition’s alternative policy to tackle climate change, called Direct Action, will be ineffective and too expensive. Labor said it couldn’t support the repeal if it was to be replaced by the government’s direct action plan.

“Without a credible alternative, Labor cannot support the abolition of the existing clean energy policies,” shadow climate change spokesman Mark Butler said in a statement.

The opposition is standing by its support of an emissions trading scheme, which under existing legislation isn’t due to begin until July 2015.

Greens leader Christine Milne said a price on carbon would be essential for Australia’s future and it was time the government dropped its expensive alternative for reducing emissions.

“Tony Abbott should now abandon the so-called direct action plan, which is little more than a slogan,” she said in a statement.

Environment groups congratulated the Senate, urging it to use this as a chance to negotiate with the government on a climate change policy that puts a price on pollution.

The government has been trying to pass the carbon tax repeal bills as a matter of priority since December, but has faced an impasse in the hostile Senate.