BALLOTING of refuse collectors for strike action in a row over pay will start on May 31.
The ballot has been prompted by what the Unite union says is an "insulting" pay offer to workers in Croydon and Bromley.
Voting will be held over 14 days and Unite expects to announce the result around June 14.
Veolia, which runs the refuse collection services in the boroughs, has offered its staff in Croydon a 1.75 per cent pay rise, with two per cent being on the table in Bromley.
The union is looking for a deal at least in line with the 3.3 per cent inflation rate.
Unite has around 50 members in Croydon and more than 120 in Bromley.
Union spokesman Onay Kasab said he was confident of a majority in favour of action in both boroughs.
The union intends the action to cause as much disruption as possible.
It will be coordinated across both boroughs to ensure staff cannot be moved between Croydon and Bromley to cover for striking colleagues.
Veolia issued a statement after the ballot was first announced regretting that action was being considered before negotiations had run their full course.
While the union is willing to talk, Mr Kasab said: "I am not interested in cosy talks over tea and biscuits.
"Our members' pay is the priority."