Hospital casualty departments are facing a staffing crisis as a growing number of doctors become GPs, the British Medical Association is warning.
General practice is benefitting from an exodus of casualty staff, experts claim
It said 62% of accident and emergency units have lost a staff grade doctor to general practice in the last year.
Concerns about the situation will be aired at a BMA conference in Edinburgh on Monday.
BMA spokesman Mohib Khan will demand new contracts in a bid to tackle low morale caused by the pay gap.
Staff grade and associate specialist (SAS) doctors comprise about half of the doctors in A&E departments, excluding trainees.
These doctors often receive little or no extra pay for working antisocial hours.
The BMA's research, compiled from a survey of 138 hospitals, found that seven in 10 A&E departments had vacancies for staff grade doctors.
Three quarters of people interviewed complained about the inequality of pay between casualty department doctors and other medical staff, such as out-of-hours GPs.
Although the NHS Employers' Organisation is preparing to negotiate with the BMA on new contracts, no deal can be clinched until the go-ahead is given from government health officials.
Mr Khan, chairman of the BMA's staff and associate committee, said: "Unless things get better for this group of doctors, there are going to be serious problems staffing hospital emergency departments.
"The BMA has always had concerns that poor conditions for staff grade and associate specialist doctors would be bad news for patients.
"This is evidence that their neglect poses a real threat to accident and emergency services."
Mr Khan will also underline what he claims is a problem of bullying, highlighted by casualty medics as a major source of stress.
He will tell delegates at the Recognition and Reward conference they are often assigned demeaning and inappropriate tasks, denied career progression and refused access to training.
Health Minister John Hutton said: "It is nonsense to suggest that there is a crisis in recruitment and retention in A&E departments.
"Since 1997, there has been a 50% increase in the number of associate specialists in A&E together with a 55% increase in A&E consultants.
"Because of the increase in the number of doctors and nurses more patients
are being seen more quickly in NHS A&E departments than ever before."