Bahrain's main Shia opposition party, Al-Wefaq, will boycott next month's by-elections to replace members pf parliaments who resigned in protest against government crackdown on demonstrators in March, a party official has said.

The party "has decided to boycott the by-elections" to be held on September 24 to replace its 18 MPs who walked out in February, shortly after a month-long anti-government protest began, Khalil al-Marzouk, a party official, said on Saturday.

"Our decision is final. We will not participate in this parliament," Marzouk said, according to a transcription of his address forwarded to AFP by the party.

He said the 40-member parliament had lost its legitimacy since the mass resignation, and "we will not be a part of this parliament as it does not represent the will of the people".

In March, parliament accepted the resignation of 11 of the 18 Al-Wefaq MPs who stepped down after security forces killed seven protesters as authorities in the kingdom ruled by a Sunni dynasty sought to curb protests inspired by uprisings that toppled Egypt's and Tunisia's presidents.

On March 16, security forces drove the mostly Shia protesters out of central Manama's Pearl Square and demolished their camp after King Hamad bin Isa al-Khalifa declared a state of emergency and called in Saudi-led Gulf troops to boost government forces.

The Bahrain authority say 24 people, including four policemen, have been killed in the unrest.

Al-Wefaq also disputes the legitimacy of the upper house of parliament, whose 40 members are appointed rather than elected, and can block initiatives of the lower house.

The party has rejected the outcome of a national dialogue held in July at the initiative of the king to re-launch a process of political reform in Bahrain.

The party had withdrawn from the talks demanding a representative, elected parliament, a fair justice system and security for all in Bahrain.

At least 500 people have been detained in Bahrain since the protests broke out in the Gulf kingdom, according to Amnesty International.

Almost 2,000 people have been dismissed or suspended from their jobs on the suspicion that they participated in the anti-government protests, it said.

Source: Al Jazeera and agencies