The Socialist Forces Front (FFS) joined on Saturday a growing list of parties calling for a boycott on 8 April.
This would be a repeat of 1999 when all candidates apart from Abd al-Aziz Boutaflika, backed by the powerful military, pulled out, citing fraudulent conditions.
President Boutaflika, a former foreign minister, has pledged a free and fair ballot. He recently invited foreign election observers and called on state media to give candidates more air time on radio and television networks.
'Serving the regime'
"The FFS considers it politically irresponsible and morally indecent to go ahead with an election that only serves the regime, the mafia circles and those benefiting from the oil sector," the FFS said in a statement received on Saturday.
Algeria is just coming out of a decade of violence sparked by the cancellation of parliamentary elections that a now-banned hardline Islamic party was set to win in 1992.
The ensuing violence, much of it at the hands of the hardliners calling for a Taliban-style state, led to the deaths of more than 150,000 people, according to human rights groups.
The United States has criticised the North African country for keeping an emergency law which bans demonstrations. It is critical of a clampdown on the independent press and for not giving the opposition more time on state media.
The move by the FFS comes only days after Mouloud Hamrouche, a former prime minister, pulled his party out of the race, saying the election would be unfair as the military had decided to back Boutaflika. He offered no evidence.
"In 1999, we realised reality on the eve of the vote, but this time the mechanisms of fraud are already clearly apparent even before the start of the official electoral campaign," Hamrouche said this week.
Violence has led to the death of
more than 150,000 people
Armed forces chief General Muhammad Lamari said recently the military, with a tradition of intervening in national politics, would stay neutral.
Quashing the press
Ali Benflis, leader of Algeria's largest party - the National Liberation Front and whose activities have been frozen by the courts - accuses Boutaflika of quashing parties and the press. An ex-premier, he has threatened to boycott the vote.
The official campaign starts one month before the vote. Boutaflika is expected to announce his candidature shortly.
He suffered a setback this week when leaders of the ethnic Berber minority in the volatile Kabylie region called for an election boycott.
Boutaflika is favoured to win another five-year term after securing the backing of the RND party of Prime Minister Ahmad Ouyahia and the allied MSP Islamic party.