Miriam Harte has resigned as the director of Beamish, the North of England Open-Air Museum, after being frustrated in her attempts to move the museum to trust status.

Harte, who had been in the role for six years, said: "Despite many efforts to raise and address key issues, I now believe that it is impossible for me to properly discharge the duties of the director of this organisation because of current structures and management arrangements, and the way in which these are exercised. I have therefore felt obliged to resign."

A joint committee, consisting of councillors from across the region and chaired by a representative from Sunderland City Council, governs the museum. Sources close to the museum said elements on the committee were reluctant to cede control to a trust.

A Sunderland City Council statement said: "We can confirm that Miriam Harte's resignation has been accepted. She is serving an agreed term of notice and we thank her for her contribution to Beamish over the past six years. While she has expressed her personal views publicly, we feel it is not appropriate to comment at this stage."

Described by one museum insider as "short, spiky and really rather good", Harte saw the museum named Large Visitor Attraction of the Year by VisitBritain, winning the English for Excellence gold award in 2005. Her resignation comes as the museum is looking to invest £40m in a new visitor centre, hotel and leisure centre.

Kevan Jones, the MP for North Durham, where the museum is located, said: "Miriam's resignation is bad news for Beamish. The council urgently needs to look at the governance of the museum. I am worried it will affect future funding and the museum's ability to find a new director."

Patrick Steel