Voter support for Daniel Andrews has collapsed in the wake of the CFA debacle, with a majority now favouring Opposition Leader Matthew Guy to lead the state.

In a finding that will send shockwaves through the state Labor government and intensify pressure on Mr Andrews over his handling of the CFA issue, Mr Guy is now leading Mr Andrews 51 to 49 per cent as preferred premier.

A ReachTEL poll commissioned by Fairfax Media has found Labor clinging to a narrow 51 to 49 per cent two-party-preferred lead, down from 52 to 48 per cent at the November 2014 state election.

The poll of 1653 voters taken on Thursday night follows a shocking week for the Premier, with former emergency services minister Jane Garrett under pressure to resign from Parliament after being accused by her colleagues of leaking to destroy the government.