Acas said in its annual report that it has dealt with 1,054 collective disputes in the past 12 months.
These included cases at British Airways, London Underground, and the airports group BAA as well as many from the SME sector.
“We’ve had another busy year,” said Ed Sweeney, Acas chairman, who added that the service received one million calls for advice.
The north west of England saw the most cases of collective disputes dealt with by Acas with 228, followed by Scotland with 220. The south west of England had the fewest cases, at 26.
Acas said nine out of 10 cases were either resolved or saw unions and companies move towards a deal.
The annual report, published on Thursday, also said that Acas dealt with almost 18,000 disputes between individuals and their employers.
Ed Sweeney said: “The success of our pre-claim conciliation service was highlighted by the government’s proposal to expand it in their resolving workplace disputes consultation.
“We know that tackling issues in the workplace as early as possible can save time, money and stress for all involved,” he said.