The recently reformed Official Republican Movement (ORM), which split last year from the Workers' Party, has welcomed the Belfast Agreement and called for a Yes vote in the referendum.
The ORM acknowledged the "courage of David Trimble in attempting to move the Ulster Unionist Party away from backwoods bigotry to the secular world".
It added: "Others who call themselves republicans should also accept that Trimble has taken massive risks for peace and that his success in persuading the UUP to back the agreement is no mean achievement."
The group attacked the "hillbilly bigotry" of the Rev Ian Paisley's DUP and loyalists "who find it mentally impossible to accept that 42 per cent of the population of Northern Ireland even exist."
