Lynch was fourth on the Green Party's list of candidates for the Top-Up (Additional Member System) seats at the 2000 London Assembly elections (11 seats elected by proportional representation). Three Green Assembly Members - Cllr. Darren Johnson AM, Cllr. Jenny Jones AM and Victor Anderson - were elected to Top-Up seats. In May 2003, Anderson resigned and was replaced by Lynch. In the 2004 London Assembly election, the Green vote share in the top-up seats election fell from 11.1% in 2000 to 8.37% in 2004, meaning that the party lost their third seat, held by Lynch, leaving Johnson and Jones as the remaining members of the London Assembly Green Group.