Lawmakers in Cambodia's new Parliament will come from only one party - the Cambodian People's Party (CPP) of long-time Prime Minister Hun Sen, the National Election Committee announced last night.

In a statement, the committee confirmed news that had long been disclosed by the CPP soon after the July 29 general election - that it had made a clean sweep of all 125 parliamentary seats.

The controversial election took place shortly after the CPP's strongest challenger, the Cambodia National Rescue Party (CNRP), was dissolved by a court, its senior members banned from politics for five years and its president detained for alleged treason.

While CNRP's political exiles urged supporters to boycott the election, the government pulled out all the stops, including ordering employers to give workers three days' paid leave, to get people to the ballot box.

In the end, 6.96 million people - or 83 per cent of registered voters - cast their ballot. But the number of invalid votes jumped from just 1.6 per cent in the 2013 general election, to 8.5 per cent, or almost 600,000, this year.

This figure was higher than the votes cast for even the best-performing opposition parties.

The royalist Funcinpec Party won 5.4 per cent, or 374,510 of all votes cast. The 13-year-old League for Democracy Party was close behind with 4.4 per cent.

In contrast, Khmer Will Party received just 3 per cent. It was formed just this year by Mr Kong Monika - whose father and brothers belong to the banned CNRP - to provide an alternative for CNRP supporters.

The CPP won more than 4.8 million votes, or 77 per cent of the valid ballots.

While many regional countries have accepted the poll outcome, Japanese Foreign Minister Taro Kono told his Cambodian counterpart Prak Sokhon earlier this month the results were disappointing and noted that many of the ballots were judged to be invalid, according to Japanese broadcaster NHK.

Both the United States and Europe have questioned the credibility of the election, and Washington has threatened to widen visa restrictions on key officials.

In Australia, which said the election "reversed more than 25 years of progress towards democracy in Cambodia", Foreign Minister Julie Bishop yesterday met Ms Kem Monovithya, the daughter of jailed opposition leader Kem Sokha.

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Dr Deth Sok Udom, a Phnom Penh-based academic, expects the West to have shrinking leverage on Cambodia. "If the West pushes for more sanctions, it will drive Cambodia deeper into China's orbit; if the West doesn't follow through the threatened sanctions, Cambodia will call the West's bluff," he told The Straits Times.

Analysts expect Mr Hun Sen, who has been in power for over three decades, to ease one of his children into leadership. His eldest son, Lieutenant-General Hun Manet, is the deputy commander of the armed forces. Middle son Hun Manith heads the defence ministry's powerful intelligence unit. His youngest son, Mr Hun Many, is a legislator and runs the CPP's youth wing.

Dr Udom added that the CPP's victory may, on the other hand, also push it towards reform: "There will be less formal checks and balances within Parliament... CPP's legitimacy will rest entirely on its performance and ability to provide better services.

"Presumably, there will be more younger, and hopefully, more technocratic appointments in the Cabinet, to sustain growth and pave the way for a smooth power transition for the younger generation of CPP leaders."

Mr Hun Sen said yesterday he will set up a consultation forum that will let the government gather input from all political parties, to further develop the country, the Khmer Times reported.