About 2,000 senior NHS doctors have written to Prime Minister Theresa May to urge her to increase spending on health and social care.
The letter – read and signed by NHS consultants, associated specialists and GPs – is due to be posted from Brighton at 14:00 GMT on Thursday.
It reads: “We have reached unacceptable levels of safety concerns for our patients within the NHS.”
A government spokesman said it was committed to investing in the NHS.
The letter was organised by emergency consultant Dr Rob Galloway and consultant anaesthetist Anita Sugavanam, both doctors at the Brighton and Sussex University Hospital NHS Trust.
The clinicians said it was a letter they hoped they would “never have to write”, but they feared a “brain drain” from the health service.
“We are constantly failing to meet our own and our patients’ expectations,” they wrote.
“We apologise to them and we also empathise with them. We feel handcuffed and paralysed working in this current NHS.
Full story on The BBC, 8 February 2017