Labour must end the trade unions' "abuse and inappropriate" influence over its leadership selection process, Peter Mandelson has said.
Appearing on the BBC's Andrew Marr Show, the former minister also called for an end to the party's "unhealthy" dependence on trade union funding.
Lord Mandelson said the unions have an important role to play in society and politics but added: "I am not happy with a Labour Party so clearly dependent on people who pay the piper and then in many cases can call the tune.
"That's not a good look, that's not right for a Labour Party appealing for votes in the 21st century."
Former Treasury minister admits he had been "burnt with the shame of it" every day since he left the note for his Lib Dem successor in 2010.
Writing in the Observer the former leader said the party had to show it stands for "ambition and aspiration" as well as compassion and care.
Former Cabinet minister Lord Hutton wants the leadership role to be given to one of the party's up-and-coming members of parliament.