Staff have accepted real terms pay cuts for three years while accounts show partners have taken millions
GMB Union is calling on Thompsons solicitors to set a date for meaningful last ditch talks to avoid national strike action.
Members are currently set to stage a national walk out over pay on the October 18.
Picket lines expected at the firms offices in Bristol, Plymouth, Cardiff, Birmingham, Stoke, Leeds, Manchester, Liverpool, Belfast, Congress House (London), Condor House (London), Dagenham, Norwich and Newcastle.
GMB members voted 89% in favour of taking action on a turnout of nearly 73% after the firm made an original offer of 1%, followed by a revised offer of 2% after talks at ACAS.
Nadine Houghton, GMB National Officer, said:
"The ball really is now in Thompsons’ court.
“We wrote to the firm on Friday with a list of dates we are available and a list of questions we have about the accounts.
“GMB hopes Thompsons can be transparent and give us some clear cut answers as well as scheduling urgent talks to avoid strike action.
"Our members have been very reasonable for a number of year. They have accepted below inflation pay increases only to find that equity partners have taken millions in drawings on profit.
"The strength of feeling from the members is loud and clear but we genuinely hope that strike action can be avoided and remain available for urgent talks."