John Prescott used his first official outing since losing his department to stress his continuing role in brokering deals on thorny policy issues.
Mr Prescott: Lost department in reshuffle
The deputy prime minister has come under fire for keeping his salary and grace-and-favour homes despite no longer having a department to run.
He told Labour's Let's Talk event that departments must work together on issues like climate change.
Tony Blair had asked him to "negotiate solutions" to difficult policy areas.
Mr Prescott has insisted he talked to the prime minister about dropping his department before the furore over his affair with his diary secretary, Tracey Temple.