Prominent opposition figure Kem Monovithya met with officials in Japan last week, urging the nation to take a stance against what she described as Prime Minister Hun Sen’s increasingly authoritarian regime.

She arrived in Tokyo on Wednesday, speaking to members of Japan’s bicameral legislature on Thursday. Monovithya urged the lawmakers to pressure the government to take action. “The Cambodian people are deprived of their right to choose their future, meaning they are deprived of their right to free and fair elections,” Monovithya said in a video posted by NHK World, Japan’s public broadcaster.

Monovithya’s father – opposition President Kem Sokha – was arrested on widely dismissed charges of “treason” in September. His Cambodia National Rescue Party, which was seen as the only viable challenger to the ruling Cambodian People’s Party, was subsequently forced to dissolve.

Condemnation of the crackdown was almost universal, with both the US and the EU pulling funding for the upcoming July elections. Japan, however, has remained one of Cambodia’s only democratic allies and continues to fund the National Election Committee.

In the NHK clip, Monovithya called the upcoming polls “a sham, fake election”.

“What is Japan’s position?” she asked, adding that the country “has to make a decision”.

CPP spokesman Sok Eysan derided Monovithya’s international campaign for support for the former CNRP, claiming it has been ineffective overall.

“They have been around the world. Next will they go to the moon and Mars?” he asked.

Eysan said the opposition was barking up the wrong tree, claiming Japan supports Cambodia and the “rule of law”.

He added that, despite effectively being a one-horse race – the second-most prominent party involved, Funcinpec, failed to win a single seat in 2013 – the elections will be free and fair and Japan’s funding would ensure that.

Despite Japan’s reluctance to criticise Cambodia, Japanese officials did urge Hun Sen to reopen dialogue with the opposition, a suggestion that was firmly rejected.

Political analyst Hang Vitou said Japan has “its own strategy to help Cambodia”. Vitou said he believed Japan will use its position as a major investor and aid donor to influence Cambodia, without coming on too strong. “Most of the EU countries, they force Cambodia to do this and that. The government, having real sovereignty, will not follow orders,” he said.

However, Vitou said the government may listen to appeals for compromise from a country whose support it still values.

The Japanese Embassy declined to address the matter in detail, saying via email that they could not comment on Monovithya’s “private visit”.