Unison, Britain's biggest union, will denounce "reactionary" government policies and debate demands for the prime minister's resignation at its annual conference beginning tomorrow.

But Dave Prentis, the general secretary, has urged delegates to focus on the bigger picture.

"I have no interest in the cult of the personality," he said. "My job is to represent our members and work with the government, whoever leads it. The big issues are public services, racism, pensions and our relations with the government.

"The issue for us is not about personality or personal blame, it's about our relationship with Labour and ensuring that we take our policies into the party and into the government."