Former Baywatch star Pamela Anderson has penned a furious open letter to the Australian prime minister Scott Morrison, calling him “smutty”, “lewd” and questioning his “strength and conviction”.

Writing on the US website the Daily Beast, Anderson criticised Morrison’s response to her calls for the government to help WikiLeaks founder Julian Assange return to Australia, accusing him of trivialising the issue.

Anderson – a close friend of Assange’s – appeared on 60 Minutes Australia earlier this month to urge Morrison to “defend your friend, get Julian his passport back and take him back to Australia and be proud of him, and throw him a parade when he gets home”.

Assange, who has been holed up in Ecuador’s embassy in London since seeking asylum in 2012, is under investigation by US law enforcement agencies for publishing classified diplomatic cables and other secret government records.

Morrison was asked about the issue in an interview on commercial radio earlier this month. When asked if he would take Anderson’s advice and throw Assange a parade, he replied: “Well no, first of all, but next, I’ve had plenty of mates who’ve asked me if they can be my special envoy to sort the issue out with Pamela Anderson.”

Anderson wrote: “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.

“We all deserve better from our leaders, especially in the current environment.

“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.”

Assange, Anderson wrote, “is not getting a fair go; his human rights are being openly violated”.

“I am hopeful Australia now has a leader with strength and conviction enough to bring him home,” she wrote.

“Australia and the world are watching how you treat your citizen, your publisher, in dire need of help from his own government.”

Assange took refuge in the Ecuadorian embassy six years ago after British courts ordered his extradition to Sweden to face questioning in a sexual assault charges.

The case was eventually dropped but Assange has remained in the embassy because of concerns he would be extradited to the US.

However his relationship with the embassy has deteriorated significantly since then.

Last month he launched legal action against the Ecuadorian government over new house rules at the embassy which limited his wifi access and ordered him to clean his bathroom and take better care of his cat. Assange said the new rules “violate his “fundamental rights and freedoms”.

Then last week court filings suggested Assange has also been criminally charged in secret by the US justice department.

The 47-year-old Australian is also ensnared in the investigation into Russia’s interference in the 2016 US election, due to his website’s publication of tens of thousands of emails stolen by Russian hackers from Hillary Clinton’s presidential campaign and other Democrats.