A federal lawsuit brought by a group of California children who claimed the US government was harming them by failing to clamp down on pollution has been tossed out by a judge.

The case was one of a series of legal actions taken around the world by young people worried about the effects of climate change.

The youths, aged between eight and 17, had claimed the US Environmental Protection Agency "intentionally allows life-threatening climate pollution to be emitted by the fossil fuel sources of greenhouse gases it regulates, harming children's health and welfare."

The suit, filed on December 10, asked the federal court to declare the EPA had violated the plaintiffs' constitutional rights to equal protection under the law and their fundamental right to life.

But a federal judge on Wednesday dismissed the lawsuit, saying the children could not make their case.

"Here, plaintiffs' claimed injuries include 'a lifetime of harms and hardship,'" said US District Judge Michael Fitzgerald in his ruling in Los Angeles.

But they "have failed to demonstrate how a declaration regarding plaintiffs' rights under the Constitution and the legality of defendants' conduct, on its own, is likely to remedy these alleged injuries."

Our Children's Trust, a non-profit that helped bring the case, slammed the judge's decision as "unjust and dangerous."

"When presented with a constitutional violation, there is no reason for a federal judge to throw up his hands and say nothing can be done," said the organization's co-executive director Mat dos Santos.

"In doing just that, this order tells children that judges have no power to hear their complaints.

"Courts do, in fact, have that power. Courts have a responsibility to hear constitutional violations, as they've done in many important cases in our nation's history."

Dos Santos said Our Children's Trust would file an amended complaint.

The case in California comes after the European Court of Human Rights in September began hearing a complaint brought by six Portuguese youths against 32 nations they accused of not doing enough to stop global warming.

In August, a court in the US state of Montana ruled in favor of a group of youths who accused the state of violating their rights to a clean environment.

That case, which also involved Our Children's Trust, is being appealed by Montana's attorney general.

Our Children's Trust has previously also launched cases in Hawaii, Utah, Virginia and Oregon.