The turmoil is the latest to envelop the Mid Yorkshire Hospitals NHS Trust, which runs health services in Wakefield, Dewsbury and Pontefract.
It follows the discovery of a £20m financial black hole at the trust shortly before Christmas despite previous claims it was on course to break even.
Chief executive Julia Squire left shortly afterwards and chairman Ed Anderson, the former boss at Leeds Bradford Airport, quit in February.
The trust faces a £26m deficit in 2012-13 and a controversial upheaval of its services as it struggles to get back into the black.
Now all four non-executive directors on the trust’s board – Anita Fatchett, David Longstaff, Margaret Faull and Iain Wilkinson – have resigned.
Interim chairman David Stone said they had collectively decided to stand down.
He said they felt unable to remain in office after considering the continuing impact of the poor financial performance of the trust. Investigations had confirmed the finances were considerably worse than had been reported to the board and the trust was unable to meet the agreed plan to achieve foundation trust status by 2014.
He added: ‘The role of a non-executive director in the NHS carries with it the responsibility of ensuring effective use of public funds as well as overseeing the delivery of high quality services.
“My non-executive colleagues have taken this decision in the best interests of the trust and I respect the integrity they have shown in taking this action.
“In accepting the immediate resignation of the four non-executive directors currently in post, I would like to acknowledge the time and commitment each of them has given to the trust, some of them over many years.”