“The state of California has veered outside of its proper constitutional lane to enter into an international emissions agreement.

“The power to enter into such agreements is reserved to the federal government, which must be able to speak with one voice in the area of US foreign policy,” said Assistant Attorney General Jeffrey Bossert Clark said in a statement.

The Justice Department said California, state officials, the California Air Resources Board, and the Western Climate Initiative Inc entered into a complex, integrated cap-and-trade programme with Quebec in 2013 without congressional approval.

In cap and trade markets, governments set a steadily declining limit on emissions, and polluters that cut emissions quickly can sell credits to others that need more time.

The pact between California and Quebec is called the Western Climate Initiative.

In its latest confrontation with California over the state’s aggressive approach to combat air pollution and climate change, President Donald Trump’s administration is arguing that the constitution prohibits states from making treaties or pacts with foreign powers.

Trump, a Republican who questions the science behind climate change, has eased regulations on the oil, gas and coal industries and intends to pull the United States out of the 2015 Paris agreement on climate change.

Last month, the Trump administration sent a letter to Governor Gavin Newsom, a Democrat, accusing the state of violating clean water laws.

Hundreds of former US Environmental Protection Agency employees are urging a congressional probe into whether the agency’s feud with California represents retaliation for the state’s failure to support Trump’s political agenda.