Strike action could be called after the result of a ballot of around 3,000 hospital workers is announced later today.
Unison has balloted all its members at Mid Yorkshire Hospitals Trust in a dispute over redundancies and pay cuts.
Nine days of strike action and protests have already been held after admin and clerical staff were told to accept pay cuts of up to £2,800.
Hundreds of staff took part in the strikes last year, but today’s result could see an escalation of the action at Mid Yorkshire, which runs Pinderfields, Pontefract and Dewsbury hospitals.
Talks to find an alternative to the pay cuts broke down in March.
And earlier this month industrial relations worsened when Mid Yorkshire announced plans to cease paying for union staff to represent their members - an arrangement common in public sector organisations.
Union’s Adrian O’Malley, the trust’s full-time convenor, and staff-side secretary Maria Thompson, of the Unite union, are at risk of redundancy under the proposals.