Managers should prepare themselves for a period of industrial unrest if planned spending cuts go ahead, Unison general secretary Dave Prentis has told HSJ.

In an interview, Mr Prentis outlined the tough approach his union will be taking against the Conservative and Liberal Democrat coalition, saying “we’ve got a fight on our hands”.

He said: “We will not let chief executives or politicians off the hook. We will make them justify everything that they do.”

Union representatives are being trained to challenge spending decisions taken by individual trusts, and communities are being mobilised in “the biggest campaign this country has ever seen” to support public service workers, he warned.

Any attack on public sector pensions – which the new government has already announced will be subject to an independent review – is likely to spark national industrial action, potentially a strike, he said.

Mr Prentis questioned the need to make £20bn of efficiency savings over three years, saying less privatisation and more progressive taxation would free up funds for the health service.

Asked how he would work with the new coalition, he said: “With great difficulty if they keep to the Tory agenda of making cuts to our public services. If that’s to be the case we’re in for a period of real conflict.”

He said Unison’s relationships with local government had shown the union could work with the Conservatives, but added: “Whether we want to be part of some general way forward with the Tories and Liberal Democrats, who are espousing policies that are anathema to us, is a different issue.

“We’re not going to go cap in hand to either a Tory or a Tory clone. We have no intention of befriending them,” he said.

However, Mr Prentis stressed Unison had also “taken on Labour at every opportunity” in the past, securing victories over policies relating to procurement, foundation trusts and public finance initiatives.

He said he had no favourite among the potential candidates for Labour leader, but that key issues were trade union involvement in the party, public services, equalities and international relationships

The union will also support staff forced to endure bullying, which he said appeared to be increasingly common in the NHS.

Mr Prentis said: “Macho managers…who believe, wrongly that to earn their spurs they’ve got to have this bullying style of management, we will oppose them to the hilt.”

Two candidates from the left of the union are standing against Mr Prentis in a leadership contest currently underway, with a result expected next month.