Former Co-op Bank chairman and disgraced Bradford Methodist minister Paul Flowers left a drug charity after an investigation over claims for expenses including for travel and dining.

The Reverend Flowers resigned from the Manchester-based Lifeline Project, where he was a trustee on the board of the organisation, the charity said.

He left the charity in 2004, long before he was engulfed in allegations of illegal drug use and gay sex that led to his suspension from the Methodist Church and a growing political row over his appointment to the Co-op Bank and its close ties with the Labour Party.

Labour leader Ed Miliband has insisted the party acted with the "utmost integrity" and shadow chancellor Ed Balls, who received a £50,000 donation to his office from the Co-operative Group, said he had "nothing to hide" and Mr Flowers was not involved.

Ian Wardle, Lifeline's chief executive, said there was concern at the nature of some of the claims made by Mr Flowers during his time with the charity which amounted to between £60,000 and £70,000 spread over a five year period and included hotels and dining expenses.

He said a detailed investigation took place, partly to get clear from Mr Flowers what the purpose of a lot of these claims had been, but satisfactory answers to those questions had not been forthcoming.

Mr Warlde said: "We didn't conclude the investigation in the manner in which we wished because the Reverend Flowers resigned as chair of Lifeline during the course of this."

A Charity Commission spokesman said yesterday: "We can now confirm that the charity Lifeline Projects contacted the Commission in 2004 to inform us of concerns into expenses payments made to a former trustee. We are working to establish the details of the charity's report to us and our regulatory response."