Pamela Anderson has slammed Prime Minster Scott Morrison after he rejected her calls to help WikiLeaks founder Julian Assange come home to Australia.

In an open letter published in the Daily Beast on Sunday, Ms Anderson said Mr Morrison was "smutty", "lewd" and questioned his "strength and conviction".

The former Baywatch star had previously urged the prime minister to lend his support to Mr Assange, who has been holed up in the Ecuadorian embassy in London for six years.

Mr Morrison flatly rejected the appeal, chuckling about it on the Nine Network's 60 Minutes.

He also told Gold Coast radio station Hot Tomato FM: "I've had plenty of mates who have asked me if they can be my special envoy to sort the issue out with Pamela Anderson".

We've found the audio of Prime Minister Scott Morrison's #JulianAssange interview with Hot Tomato - "I've had plenty of mates who have asked me if they can be my special envoy to sort the issue out with Pamela Anderson” #auspol pic.twitter.com/LFiwuyBkWK — Brett Mason (@BrettMasonNews) November 6, 2018

Ms Anderson appeared to accuse Mr Morrison of sexism.

"You trivialised and laughed about the suffering of an Australian and his family. You followed it with smutty, unnecessary comments about a woman voicing her political opinion," she said in the open letter.

"We all deserve better from our leaders, especially in the current environment," she wrote.

"Rather than making lewd suggestions about me, perhaps you should instead think about what you are going to say to millions of Australians when one of their own is marched in an orange jumpsuit to Guantanamo Bay - for publishing the truth. You can prevent this."

On Thursday, US prosecutors inadvertently disclosed the existence of a sealed indictment against Mr Assange in a court filing in an unrelated case.

The exact nature of the charges against Assange was not immediately known.

AAP

Mr Assange took refuge in Ecuador's embassy in 2012 after British courts ordered his extradition to Sweden to face questioning in a sexual molestation case.

The case was dropped but supporters have said Mr Assange fears leaving the embassy in case he's extradited to the US.

Ms Anderson said Ms Assange's health has deteriorated over the years.

"For six years he has been refused any access to fresh air, sunshine, exercise, or proper medical or dental care. In February 2016, the UN Working Group on Arbitrary Detention (WGAD) stated that his detention was unlawful," she said.

"This Australian is not getting a fair go; his human rights are being openly violated."

AAP

Ms Anderson has denied rumours she was anything more than a friend of Mr Assange, but said in a recent interview they have a close bond which they describe as a "romantic struggle".

Earlier this month, an Ecuadorian judge ruled against the 47-year-old's request to loosen new conditions of his ongoing stay at the embassy.

The new rules require the Australian pay for services like internet and laundry and care for his cat.

In a video testimony, Mr Assange argued that the stricter measures were part of a larger push to kick him out of the embassy.

- Additional reporting: AAP