Labour man quits for SNP.
He blamed the party's "lurch to the right of British politics" for his decision.
It leaves the council with 29 Labour members and 29 opposition representatives.
Labour will be dependent on the casting vote of Lord Provost Lesley Hinds to carry any policies opposed by other parties.
Cardownie, 52, will be the only SNP councillor on the council.
He denied fears of deselection were behind his move and added: "I do not feel in my heart of hearts that I can any longer support the Labour administration on the council