The government has made it clear it will not back down over NHS pay, despite threats of industrial action.

Speaking to an unusually muted audience of NHS workers at the Unison healthcare conference in Manchester last Wednesday, junior health minister Ivan Lewis stressed that "turning on each other" would play into the Conservative Party's hands.

His comments came the day after the union voted to ballot members over proposals to give staff covered by the Agenda for Change agreement a pay rise of 2.75 per cent in 2008-09, 2.4 in 2009-10 and 2.25 in 2010-11.

A significant minority of delegates wanted the union to move straight to an industrial action ballot.

The minister said: "We understand that the debate was tense and there was controversy but... in the current very tight financial climate, we have done our best to achieve the very best financial deal.

"We welcome the ballot and ask you to remember that we can't change the fact that in the short term we have to function within the economic realities that we face."

On plans for an NHS constitution, Mr Lewis said it needed to enshrine staff rights such as protection from violence and aggression. Tougher sentences, using "existing or new powers", should be handed to those who attack staff, he said. In addition, employees should expect managers to be of "calibre not mediocrity".

The most audible heckling was prompted by Mr Lewis's response to a question about the pressures placed on NHS workers. He said: "We should expect, in the NHS, leaders and managers who ensure that staff don't find themselves in these circumstances."

Mr Lewis discussed other challenges facing the NHS, including rising public expectations and the increasing numbers of patients with long-term conditions.

He said it was important to make social care a priority and to reduce the variability of decisions over who is eligible for it.

He criticised local authorities that were "spending money on setting up TV stations while care home charges were going over the roof".

And the minister said opposition leader David Cameron's NHS policies were little more than a "newly discovered commitment - a cynical attempt to ensure that the NHS won't even be an issue at the next election".

Other health unions, including Unite and the Royal College of Nursing, are also consulting members over the pay deal. Unite, which has recommended that members do not accept the deal, was due to make its decision this week. The Royal College of Nursing has recommended that members should accept the proposed pay deal.