The chief executive and chairman of a Staffordshire NHS trust being investigated over higher than normal death rates have resigned.
Mid Staffordshire NHS Foundation Trust is being investigated by the Healthcare Commission over mortality rates at Stafford Hospital.
The watchdog's report is expected to be published later this month.
The trust said chairman Toni Brisby and chief executive Martin Yeates had stepped down with immediate effect.
The independent regulator Monitor has appointed David Stone, the chairman of Sheffield Teaching Hospitals NHS Trust, as the new chairman of Mid Staffordshire.
A new chief executive for the trust, which runs Staffordshire General Hospital, in Stafford, and Cannock Chase Hospital, has not yet been appointed.
The healthcare commission said last September it had been investigating Mid Staffordshire NHS Foundation Trust's death rate since March 2008.
It said it had highlighted "serious concerns about the A&E department" at Stafford, including low staffing levels, poor leadership and the structure of the department.
Figures showed the trust's standardised mortality rate (SMR) was 127 in 2005/06. Nationally, it is set at 100.
The trust said its SMR was down to 101 between May and October 2007, with an SMR for emergency admissions over that time period of 100.4.
The trust said the apparently high mortality rate was due to problems in the way it was "recording and coding information about patients".
In a statement, the trust said on Tuesday that Ms Brisby and Mr Yeates had stepped down "to enable the trust to build on the considerable improvements that have been made over the past 18 months".
It said this included improving the A&E department, recruiting more doctors and nurses and reducing infection rates to below the national average.
Ms Brisby said "It is with great sadness and reluctance that I have made the decision to step down as chair, from what I consider now to be a transformed organisation from the one I joined in 2004."
Mr Yeates said he had not taken the decision to resign "lightly".
He said a new management team and 100 new nurses had been appointed.
He added: "I recognise that there is still a lot to do. I am very proud of what we have achieved so far.
"The organisation is now in a stronger position and I have developed an experienced management team that can take the trust forward and continue to improve patient care for the local community".