In 2003, he left to become chief executive of the National Consumer Council, staying with the organisation for 5 years. In 2008, the National Consumer Council merged with energywatch and Postwatch to form Consumer Focus, a move which Mayo oversaw as he became chief executive of the new organisation. In July 2009, he announced that he would be resigning to take up the position of Secretary General of Co-operatives UK following the retirement of its Chief executive Dame Pauline Green. He took up the position officially the following November.