Unite’s public transport workers and police staff are set to join a major strike in Northern Ireland next week, the union has said.

Teachers, nurses, health workers and civil servants are among those who are to take part in what is expected to be one of the biggest strikes in recent history over pay.

It comes after a host of public sector workers took part in separate previous walkouts over an outstanding pay award.

Unions across sectors will join together in the “day of action” on January 18 in response to the failure to award a pay deal in line with colleagues across the UK.

Sinn Fein vice president Michelle O’Neill said public sector workers have been “forced into a horrible position” of undertaking strike action next week.

During talks between Secretary of State Chris Heaton-Harris and the Stormont parties in December, a £3.3 billion financial package to accompany the return of devolution was offered.

The package would include money to make an outstanding pay award to public sector workers.

However, with Stormont remaining effectively collapsed, that funding has not materialised.

An Northern Ireland Office spokesman previously said the package will remain on the table until a new Executive is formed to allocate it

Unite said its 8,000 public sector workers will join the strike, adding that over the next 24 hours it will provide full details of the industrial action to a range of public sector employers.

The union’s membership includes more than 4,000 health and social care workers, 2,300 bus and rail workers, 800 education authority workers as well as members in the roads service, forestry service, rivers agency, ferry services and the Police Service of Northern Ireland (PSNI).

PSNI Temporary Assistant Chief Constable Melanie Jones said planning is under way to “mitigate any risk in critical functions in the event of staff absences as a result of industrial action”.

“I want to reassure the public that we will have the resources in place to allow us to keep people safe,” she said.

Unite general secretary Sharon Graham said it will be an “unprecedented demonstration of the power of workers in Northern Ireland”.

“For almost two years, the absence of a functioning Stormont Executive has led to growing paralysis and crisis across public sector services,” she said.

“This situation has been made worse by a Secretary of State for Northern Ireland who has sought to leverage the crisis in the current negotiations through imposing a punishing budgetary settlement.

“Unite will not allow the livelihoods of workers and the funding of public services to be used as a bargaining chip by this Government.”

The GMB union said more than 5,000 of its members from the Civil Service, Education Authority, health trusts and transport sectors will also strike next Thursday.

GMB senior organiser Alan Perry said its members “have simply had enough”.

“They will not be used as political pawns in a process that would see the return of the Northern Ireland Executive,” he said.

“The Secretary of State made it clear that money is there; he must do the honourable thing and make it available now to address the concerns of members who desperately need it.”

Speaking to reporters at Belfast City Hall, Ms O’Neill said it is “not acceptable” that workers are not paid fairly.

“It’s not tolerable and it’s not the position that they should be in,” she said. “So, we fully support them in their action.

“We have had years of under-investment in this place. Just before Christmas the British Government have finally recognised that we have been underfunded.

“What we need to see now is a restored Executive and all of the parties working together. We take the financial offer and we want to add to that financial contribution because the Treasury have failed public services here.”

She added: “Public sector workers are waiting anxiously to know if they are going to get money into their pockets which they absolutely deserve. We support that.”