The workers, who are employed by Lewisham & Greenwich NHS Trust's outsourced provider ISS, have held three protests in recent weeks.

Helen O'Connor, GMB membership development officer, said: ‘Anger is mounting amongst staff in Lewisham Hospital who are fed up with ISS dragging its heels over improving pay and conditions.

‘These hardworking staff remain on poverty pay and endure harsh working conditions and they are sick and tired of empty promises being made to them that things will improve.

‘GMB members are calling on ISS and Lewisham and Greenwich NHS to table an offer that will lift these staff and their families out of poverty and improve their working conditions.'

In response, a spokesperson for ISS UK&I, said: ‘We value the contribution of every ISS team member and will continue to work towards a resolution.'

The trust was unavailable at the time of writing.