The leader of the militant construction union and one of the union movement’s most public faces, Dave Noonan, is resigning after 15 years in the position, to be replaced by a young successor.

Mr Noonan, who has been in Canberra this week lobbying the crossbench over the abolition of the building industry watchdog, told colleagues and politicians he will quit the union at the end of March after taking leave at the end of this year.