India and China joined forces on Tuesday in saying they firmly rejected the EU's "unilateral" decision to impose a carbon tax on air travel.

The European Union (EU) imposed the tax with effect from January 1, but no airline will face a bill until 2013 after this year's carbon emissions have been tallied.

"We strongly oppose the EU's unilateral trade measure in the name of climate change," India's environment minister Jayanthi Natarajan told reporters at the conclusion of the BASIC Ministerial Meeting on Climate Change in New Delhi.

The meeting was attended by representatives of the BASIC group -- Brazil, South Africa, India and China.

Earlier in the month, China barred its airlines from complying with what many opponents consider a tax.

"This decision by the EU will seriously jeopardise (our efforts to) tackle the international efforts to climate change," said China's top climate negotiator Xie Zhenhua.

The EU has said the carbon tax will help the 27-nation EU bloc achieve its goal of cutting emissions by 20 percent by 2020 and that it will not back down on the plan.

The EU argues that the cost for airlines is manageable, estimating that the scheme could prompt carriers to add between 4.0 and 24 euros ($32) to the price of a round-trip long-haul flight.

Over two dozen countries, including Russia and the United States, have opposed the EU move, saying it violates international law.