Firefighters union boss Peter Marshall has sworn on oath that there is no "secret recording" of Premier Daniel Andrews and no "secret deal" between the two men.

The union leader sent shockwaves through Victorian politics in April with an incendiary radio interview where he hinted at a secret deal with the Labor government.

But it was his repeated refusal to quash the long-running rumour of a covert recording, compromising the Premier and used as leverage in negotiations with the government, that kick-started days of controversy in Parliament and beyond.

Firefighters union boss Peter Marshall. Credit:Angela Wylie

Now Mr Marshall has sworn out an affidavit, denying for the first time the existence of the tape and that there is any “secret deal”.