Unison says 99% of its members at Serco backed walking out over plans to shift pay days from weekly to monthly, a move many say will leave them struggling to make ends meet.

Two-thirds of workers say the switch threatens to leave them in debt, according to a recent union survey.

Around 600 Serco support staff, including cleaners, caterers, security staff and porters, will be affected.

Unison claims Serco previously threatened staff with controversial "fire and rehire" tactics to impose the changes to the frequency of their pay. The company has since backed down and has offered loans to employees, but remains intent on phasing in monthly payments, Unison says.

The union is demanding a guarantee that weekly pay remains an option for all staff.

Unison Scotland regional organiser, Greig Kelbie, said: ‘Staff at Serco are tired of being pushed around. Their position is clear. This dispute continues until weekly pay remains an option for all those who want it.'

Karren Morrison, Unison branch secretary at Forth Valley Health, added: ‘Low-paid health workers should not be forced into financial hardship just to suit Serco.

‘A move to monthly pay risks pushing many into debt. Without a cast-iron commitment that weekly pay will continue, workers believe their finances remain under threat.'

In response, a Serco spokesperson, said: ‘We've met with Unison today (5 August). Our discussions were constructive, and we believe we are close to reaching an agreement.

'We reject the claim that staff are being threatened with "fire and rehire" tactics. We value our team and continue to work together to find a suitable resolution.'