Foreign Minister Julie Bishop has resisted calls to reject the Cambodian election results outright, but says Australia has "serious concerns" and has made them known to the Cambodian Government.

The Federal Government has been urged to reject the results and impose sanctions on the Hun Sen regime after his ruling party declared victory in a vote that was widely seen as a sham.

In a statement, Ms Bishop said as a "longstanding friend of Cambodia", Australia would continue to urge the Cambodian Government to take steps to allow free and open political debate without violence and intimidation.

The leader of Cambodia's main opposition is in jail, his party has been dissolved, and independent media in Cambodia is largely silenced.

So democracy activists are angry Australia strengthened ties with the Cambodian Government last October, when Ambassador Angela Corcoran clinked champagne glasses with Cambodian officials as the two countries signed a new memorandum of understanding to create new "Senior Officials Talks".

Australian Ambassador Angela Corcoran shares a toast with members of the Cambodian regime ( Facebook: Australian Embassy )

The new agreement came after Australia committed an extra $40 million in aid to Cambodia in 2014, in exchange for resettling refugees from the offshore detention centre in Nauru.

That deal is seen as an expensive failure with just three of seven resettled refugees remaining in Cambodia.

The main Cambodian opposition party, which was banned from competing in the elections, is now calling on the Turnbull Government to impose travel and asset sanctions on the Hun Sen regime.

"Our people went to the Australian ambassador in Phnom Penh and said 'Madam Ambassador, is this what Australia wants? A continued dictatorship? You must be on the side of democracy'," Mu Sochua, the deputy leader of the now-dissolved Cambodian National Rescue Party, told Four Corners.

Cambodia's Deputy Opposition Leader Mu Sochua has been forced into exile. ( ABC News: Jerry Rickard )

"I said to Minister [Julie] Bishop, 'please use visa sanctions. Please use active, concrete measures'.

"The people of Cambodia look up at the people of Australia, Australians. We envy you. You live in a world of democracy, but your government is disappointing.

"By making such a deal with the government of Cambodia, you lost so much of that respect that we give you.

"You don't drink champagne with the dictators."

'People in Australia like me too!'

Cambodian Prime Minister Hun Sen, pictured taking a selfie with a young supporter, has tried to silence his opposition. ( ABC News: Jerry Rickard )

Prime Minister Hun Sen has not been shy about bragging about his relationship with Australia.

Four Corners filmed him on the outskirts of the capital Phnom Penh, talking up his recent visit to Australia for the ASEAN conference.

"When I was in Australia, the people came and kissed me," he told an audience of workers who were all being paid to be there.

"It proved that not only the people in Cambodia like me, but people in Australia also like me too!"

Four Corners confirmed Hun Sen's relatives and political allies own properties and companies worth more than $15 million in Australia.

The program also uncovered how the long arm of the regime stretches to Australia, where Cambodians are recruited to support the ruling party, the CPP, and threatened for speaking out against it.

In the lead-up to the election, Hun Sen's eldest son Hun Manet openly recruited for the CPP and attempted to boost Hun Sen's support among Australian Cambodians and Cambodian students studying here.

"We created a force. In the beginning we had Australia, then New Zealand. We started with one person, then two and then three," Hun Manet told supporters at a function in Sydney in March this year.

"Finally, today, we have thousands which is a strong force. This is a success!"

Now Hun Manet has been named in a list of potential individuals targeted by future US sanctions.

The United States has already begun to impose visa restrictions and asset freezes on those close to Hun Sen, with wider measures currently before Congress.

Republican congressman Ted Yoho, Chairman of the House Foreign Affairs Subcommittee on Asia and the Pacific, is calling on Australia to follow the US lead and take firm action against the Hun Sen regime.

"Of course, we are going after anything they may own here. Travel exclusions and things like that," he told Four Corners.

"I would like to see Australia take a stronger stance. Come out openly and condemn the Hun Sen regime. They're not doing that."

Death threats made to Cambodians living in Australia

Bou Rachana, the wife of slain Cambodian activist Dr Kem Lay, received a death threat earlier this year. ( ABC News: Jerry Rickard )

Australia's Cambodia refugee resettlement deal is due to expire in the coming months, and Minister for Home Affairs Peter Dutton did not answer questions from Four Corners about whether the deal would be extended.

Former foreign minister Gareth Evens, who helped establish Cambodia's first democratic elections in the early 90's, believes targeted sanctions are the best way to impose pressure on the Hun Sen regime.

"The personal stuff, you know, the visa bans and so on, are probably the only game left in town," he told Four Corners.

"It really is just a question, I think of making it very clear to the Cambodian Government that their behaviour is utterly distasteful, unacceptable, and they can't expect to have a dream run internationally as a result."

Victorian council member Meng Heang Tak told Four Corners Cambodian Australians are being watched if they participate in anti-Hun Sen activities.

"People are fearful because they've been told once they engage or participate in critique of the government, they've been told, 'If you go to Cambodia, we're going to do something'," he said.

"'Be careful when you go to Cambodia, especially at the airport. You have friends and family and relatives in Cambodia; we know who they are'."

Cambodian Bou Rachana and her five sons were granted asylum in Australia after her husband, Cambodian activist Dr Kem Ley, was shot dead at a Phnom Penh service station in 2016.

In March this year she received a death threat that also named three other Cambodians living in Australia.

"I'm no longer surprised by these threats, because I have received countless threats. It doesn't worry, frighten, or surprise me. It's just normal," she said.

Hun Sen's nephew Hun To was questioned by Victoria Police over the death threat letter. Four Corners confronted him at his Melbourne home and he denied any involvement.

Children at a rally for Prime Minister Hun Sen, who has held power for 33 years. ( ABC News: Jerry Rickard )

Ms Bishop declined to be interviewed by Four Corners but a spokesperson for Ms Bishop said Australia would use future meetings with Cambodian officials to advocate for human rights and democracy.

But critics say the time for quiet diplomacy is over.

"It's all very nice and well to say that, you know, 'Oh, I'm making private representations', but you know, the reality is that Cambodia responds to public pressure, not private pressure," Human Rights Watch deputy director Phil Robertson told Four Corners.

Watch Sophie McNeill's investigation, Champagne With Dictators, tonight on Four Corners at 8.30pm on ABC TV and iview.