Duncan Swift, scourge of the supermarkets and partner at accountancy firm Grant Thornton, is leaving the business.

Swift, who was until this month head of Grant Thornton's Food and Agribusiness Recovery Group, is understood to be leaving to take up a similar role with rival Tenon. He is currently on gardening leave and is expected to take up his new role next spring.

During his time at Grant Thornton, Swift has worked primarily with food production and processing companies and has built up a strong reputation as an outspoken critic of the power of supermarket buyers and a campaigner for the implementation of a groceries ombudsman.

A regular and popular speaker at grocery conferences over the past few years, Swift argues it is not the supermarkets themselves that cause problems for suppliers but "rogue" buyers acting outside the company ethos.

"Over several years, on behalf of Grant Thornton, Duncan has successfully championed the rights of UK food producers and processors to receive more certainty in their relationships, and better terms of trade, with supermarkets," said Grant Thornton's head of food Phil Jackson.

"He has also ably demonstrated the inadequacies of the current supermarket code and the lack of effective enforcement of it. Grant Thornton will continue to champion these causes. I'm sure Duncan will too and we wish him well," he added.

A spokeswoman for the firm said it had no immediate plans to replace Swift.