Refuse staff are currently on their fourth walkout since the beginning of October.
A further strike is proposed from 5 December to Christmas Eve.
Unite had previously said a pay offer agreed nationally was not enough and some of its members were “living hand to mouth” while some were reliant on food banks.
Regional Officer Brian Troake said: “This dispute will not be resolved by wasting taxpayers’ money on costly legal challenges.
“The best way forward is for Warrington Council to get back round the negotiating table with Unite to find a solution that addresses our members’ entirely justified pay concerns.”
Warrington Borough Council said: “We continue to pursue the legal options available to us and have been in constant liaison with our solicitors.”
It added that because of the intended strike period in December it was “more important than ever” that the council continues to pursue legal action.
Unite members previously walked out between 3 and 16 October, 24 October and 6 November, and 8 and 20 November.
The current walkout began on 21 November and is due to end on 4 December.
