The FFS "cannot endorse a text that glorifies force and deprecates political mediation, consecrates impunity and amnesty, and in the end negotiates away pain and suffering", the FFS said in a statement.
The FFS "calls for an imaginative and active campaign by organisations, activists and sympathisers for a successful boycott of the vote", it said.
All Algerians "who care about peace, justice and truth (should) set themselves apart from the historic deception that only worsens the crisis."
President Abdelaziz Bouteflika, announcing the referendum in mid-August, described it as an effort to end bloodshed in the country, whose civil war, that broke out in 1992, has claimed more than 150,000 lives and cost the country's infrastructure $30 billion.
The draft calls for "concrete steps to stop bloodshed and restore peace" while banning the "exploitation" of Islam for political purposes, Bouteflika was quoted as saying.
The country's civil war claimed
more than 150,000 lives
Bouteflika launched a "civil reconciliation" initiative at the start of his first five-year term in 1999, leading to a partial amnesty for thousands of Islamist rebels who laid down their arms.
The programme was endorsed overwhelmingly in a referendum in September that year, and Bouteflika was re-elected in 2004, largely because the peace initiative helped quell the fighting.
The new plan provides for proceedings to be dropped against people being sought in Algeria or abroad or who have been sentenced in their absence, if they turn themselves in to the authorities and provided they were not involved in bloodshed or rape.
The president first proposed the new reconciliation programme in November, when families of those killed in atrocities during the war objected to allowing the perpetrators to escape justice.
Humanitarian and human rights groups that visited Algeria in May and June also voiced reservations over a possible general amnesty.
"The draft charter for peace and national reconciliation ... is an act of war against society which will deepen hatred and resentment"
Socialist Forces Front
The FSS statement said: "The draft charter for peace and national reconciliation ... is an act of war against society which will deepen hatred and resentment."
The text "is no more than a strategy aimed at those among national and international public opinion which are still prepared to be manipulated and fooled, that consists of absolving the guilty of crimes and incriminating the victims, and confusing the causes and the effects of the Algerian crisis," the FFS said.
It provides for legal proceedings to be dropped against Islamic extremists who ended armed activities and surrendered to authorities after 13 January, 2000, when the initial legislation on "civil reconciliation" took effect.
Algeria's Islamic insurgency was sparked in 1992 after the army prevented an Islamic party from taking power by calling off the second round of general elections it was poised to win.
The civil war reached its height in the 1990s, but officials now say that one of two main insurgent groups has been smashed and the other - one reportedly with ties to al-Qaida - is facing defeat.