Health workers have heckled a minister as he addressed delegates at a conference amid threats by staff that they will take industrial action.
The government wants to stage the pay rise
Health Minister Andy Burnham faced a wall of silence as he stood up at Unison's health conference. He was then heckled and booed during his speech.
Earlier, delegates at the Brighton meeting had rejected a staged 2.5% pay rise and agreed to ballot members.
They warned of co-ordinated action leading to a "summer of discontent".
The Society of Radiographers has also voted to consider industrial action if the government does not reverse its decision to stage the awards.
Both bodies earlier said members were "getting angrier by the day" at a below-inflation offer that they said amounted to a pay cut.
Unison leaders will now demand a meeting with Chancellor Gordon Brown to demand the pay offer be improved, and not staged.
The conference unanimously agreed that a ballot of the union's 450,000 NHS members would be held unless the offer was increased.
The union represents nurses, ambulance crews, paramedics, occupational therapists and clerical staff.
The moves come after nurses in the Royal College of Nursing (RCN) also threatened to take industrial action, in a vote at their conference last week.
The government has offered health workers in England, Wales and Northern Ireland a 1.5% pay rise this month with another 1% to come in November. Unions say this is the equivalent of a 1.9% pay increase.
Visitors sitting in the public gallery of the hall heckled the minister within minutes of him starting to speak and were warned by the conference chairman that they would be told to leave if they did not stop disrupting the speech.
Mr Burnham acknowledged that the decision had disappointed workers but said it was taken with the broader interests of the economy in mind.
But he maintained that the NHS was a better service than when Labour came to power in 1997, although he acknowledged that staff had faced a "difficult time" over the past year.
"We know we have asked a lot of NHS staff in the last 12 to 18 months to get the NHS back to financial balance.
"Of course there are differences - some of those are on display in the hall today - but let us not snatch defeat from the jaws of victory."
One delegate told the minister that staff at Whipps Cross Hospital in east London were under intense pressure because hundreds of jobs had been axed to balance the books.
The delegate said the hospital was on its knees.
However, Mr Burnham was given a warm reception for announcing the government had decided not to outsource work from the NHS prescriptions and pricing department.
Unison had feared that the entire service could be switched offshore with the loss of up to 2,500 jobs in centres including Newcastle upon Tyne, Yorkshire and Humberside.