The accuracy of tests carried out by Atos Healthcare to determine whether people are eligible to claim disability benefits has been put in doubt.
A government report revealed that up to 40% of people tested by Atos Healthcare might have been wrongly passed as fit to work.
Following the government announcement that many of the tests were below the expected standard, the Department for Work and Pensions will use more suppliers alongside Atos Healthcare to administer the work capability assessment (WCA).
Atos, through its healthcare arm, uses logic integrated medical assessment (LiMA) software to support medical professionals when assessing claimants.
Campaigners have for years claimed that many people have had their benefits cut inappropriately because of the system that Atos uses when assessing them.
In 2011, a critical report from a House of Commons Select Committee found that tens of thousands of sick and disabled people had been wrongly declared "fit for work" by the French-owned outsourcing company. Appeals are estimated to cost the taxpayer around £50m a year, said MPs.
In August 2011, two Atos Healthcare employees were investigated over allegations they made inappropriate remarks on Facebook about the people they assess for sickness and disability benefits, and are accused of separately referring to them as "parasites" and "down and outs".