SNP MSP has opened up a major rift in the nationalist movement by saying he will help launch a new independence party.Dave Thompson will quit the party after 55 years to help launch a new pro-independence outfit for the Holyrood election in 2021.The SNP veteran predicted the “Alliance for Independence” (AFI) could win up to 24 seats next year.He revealed the slogan would be “max the Yes” and added: “Just imagine 20 Margo MacDonalds in the parliament?”Get all the top Scottish politics news sent