KEVIN Rudd has pledged his Government will make a decision on a dump site for nuclear waste based on science.

"There's an independent, scientific process under way," the Prime Minister said on a visit to Darwin yesterday.

"We'll respond to the science on these questions."

Anti-nuclear and environmental groups are concerned that the Government intends to renege on its election commitment to repeal the legislation that allows the commonwealth to override state laws banning the building of nuclear waste dumps.

Eleven groups have written to Mr Rudd and federal Resources Minister Martin Ferguson demanding to know if the Government will honour its election commitment to repeal the Commonwealth Radioactive Waste Management Act, passed in 2005.

More than six months after the Government won office, Labor's promise to repeal the act has "not been publicly reiterated", the letter says.

But a spokesman for Mr Ferguson said yesterday the Government did intend to repeal the law, in line with its election commitment.

"It's all on the record, it's an election commitment," the spokesman said.