The NHS is bracing itself for a strike after its largest union voted to ballot its members over industrial action to protest against the axing of health staff's planned 1% pay rise.

Unison, which represents 400,000 NHS personnel including about 100,000 nurses, decided on Tuesday to ballot over strike action or action short of a strike.

But at least 500,000 NHS staff will be balloted after Unite, which represents another 100,000 workers, confirmed that it too will hold a ballot for action including a strike.

Unison members are "incredibly angry" about health secretary Jeremy Hunt's decision last month to cancel an across the board increase for all staff recommended by the NHS pay review body, said Christina McAnea, the union's head of health.

"We are the largest health union and we take the responsibility that comes with that very seriously. Members neither strike often or easily," McAnea told Unison's health section's annual conference in Brighton.

"But this time it feels that we have no choice. We face a government in England deliberately provoking us into a dispute and so no doubt already preparing for this," McAnea added.

NHS staff face having their pay and conditions reduced because the government is cutting NHS funding, despite pledges to protect it, she said.

Hunt has offered to endorse a 1% rise in consolidated pay if unions agree to a one-year freeze in the increments – small uplifts worth up to 7% of salary in some cases – which many staff receive as they extend their skills and experience.

Unions representing doctors and nurses are also furious about not receiving a real-terms pay rise for the fourth year in a row because of Hunt's decision.

The British Medical Association warned Hunt last month that there was "a deep sense of outrage felt by many doctors" at his refusal to give them and dentists the 1% rise in basic pay recommended by the independent body which traditionally sets the pay increases they receive.

But NHS Employers, which represents hospitals and other employers, said any withdrawal of labour would be "deeply distressing" for patients and urged unions to talk, not strike.

Dean Royles, its chief executive, said that while he understood staff's unhappiness, "my simple, honest ask is that they don't take that displeasure and frustration out on patients. People accessing healthcare are often at their most vulnerable and the very prospect of strikes when they should be receiving care will be deeply distressing for many."

Unions plan a day of action, though not involving industrial action, on 5 June as the start of a campaign against the pay deal.