A union has claimed patients are being put at risk at a city hospital because cleaners are working when they are ill.
Andy Straker, from the Unison union, said members held a protest outside Southampton General Hospital because they are not entitled to sick pay.
The union said workers had found themselves working when sick because they could not afford to take time off.
Southampton University Hospitals Trust said it was in the process of improving cleaners' pay, terms and conditions.
Unison said the pay situation contradicted the objectives of the Agenda for Change contract, set up in 2004, which was created to improve NHS workers' pay in England.
Cleaning staff at the trust's five hospitals have been provided by the contractor Medirest since the late 1990s.
In a statement, the trust's chief executive officer Mark Hackett said: "In discussion with Medirest and unions, the trust has agreed to provide funding to uplift both the pay and the terms and conditions of our cleaners to the level they would achieve as NHS employees under Agenda for Change.
"We are currently in the second year of a three-year agreement to deliver the full effect of this improvement for these Medirest staff by April 2011.
"This agreement means the trust is investing £900,000 over three years to increase rates of pay for these staff in what is now a very difficult economic environment."
But regional organiser Mr Straker said: "Our campaign is to try to get the cleaners on the same pay and conditions as everyone else within the NHS.
"Our argument is that [the trust] should have been paying that [money] since 2006 so they should give them back-pay."
Mr Hackett added: "We have seen infection rates fall dramatically [since the late 1990s], part of which is due to improved cleaning services and we have been increasing our investment in this area for the last three years."