Staff at a health trust have voted to strike over plans to move jobs to a new company.
Wrightington, Wigan & Leigh Foundation Trust is proposing to transfer catering, cleaning and portering roles to a company called WWL Solutions, which is owned by the trust.
About 600 workers will walk out on 23 and 24 May, the Unison union said.
The trust said it was "disappointed" and had assured staff they will retain NHS pay, terms and pensions.
A spokesman said: "We acknowledge and respect that staff have concerns about these proposals."
ACAS had been to help resolve the dispute, he added.
The trust runs Wigan's Royal Albert Edward Infirmary, Leigh Infirmary and Wrightington Hospital as well as the Thomas Linacre Centre and Wigan Eye Unit.
Sean Gibson, of Unison, said the "outsourcing" plan was "not necessary" and staff wanted to be allowed to continue working directly for the NHS.
NHS Providers, which represents hospital, mental health and ambulance trusts, says benefits of setting up wholly owned subsidiaries like WWL Solutions include achieving change more quickly, along with "greater scrutiny and accountability".
Mr Gibson, the union's north west regional organiser, said staff were "very upset and angry".
"They do not want their employment to be shifted to an outsourced company," he added.
The ballot saw 89% of members back strike action, with a 73% turnout.
The union said the trust had sought to justify the plan as a "necessary cost-saving initiative" despite operating with a surplus of £8.6m.
The trust said the strikes could cause "some disruption to services" and, where possible, it advised patients to make alternative plans.
A final decision on the proposals has been delayed until June.