Cambodian Prime Minister Hun Sen said Wednesday that the opposition party should not join the general election on July 28 if it does not recognize the upcoming election results.

"The election has not started, but you have already announced not to accept the results. I urge you to boycott the election if you are brave enough because you do not recognize the results, why do you join it?" the premier said during the inauguration of a school building in Kandal province.

The premier made the remarks after Kem Sokha, vice president of the main opposition Cambodia National Rescue Party (CNRP), said on Saturday that the party would contest the forthcoming election, but it would not accept the results of the election because of fraud, disruptions, and discrimination.

"Even though you do not join, the election will be held as schedule -- no your party, but 7 other parties still join the race, " said Hun Sen, who has been in power since 1985.

The premier also appealed to the opposition party's supporters to vote for his Cambodian People's Party or other parties, rather than the opposition party.

CNRP spokesman Yim Sovann said Wednesday that a boycott of the forthcoming election is still an option and called for the electoral reforms and the return of the party's self-exiled leader Sam Rainsy.

Sam Rainsy, 63, fled the country in late 2009 before Cambodian court sentenced him to 11 years in prison in absentia for two charges -- removing border poles and publishing a false map of the border with Vietnam and accusing deputy prime minister and foreign minister Hor Namhong of being a member of the Democratic Kampuchea.

The CNRP was formed in September last year by the amalgamation of two opposition parties -- the Sam Rainsy Party and the Human Rights Party.

The country is scheduled to hold a general election for its 123- seat parliament on July 28, 2013, said the National Election Committee. Some 9.67 million Cambodians are eligible to cast their ballots.

Eight political parties will run in the election. Three major parties among those registered parties are the ruling Cambodian People's Party, the CNRP, and the royalist Funcinpec Party headed by Princess Norodom Arun Rasmey, the youngest daughter of late King Father Norodom Sihanouk.

In the last election in 2008, the ruling party won 90 seats out of the 123 parliamentary seats, the opposition totally won 29 seats, and the royalist group four seats.