(Corrects para 8 of FEB 13 story to show evidence was collected from 30 warders not prisoners, and also corrects spelling of Mangaung)
JOHANNESBURG, Feb 13 (Reuters) - Security firm G4S Plc (LSE: GFS.L - news) on Friday denied allegations by former prisoners in South Africa that members of the British group's staff had tortured them.
A legal document seen by Reuters showed British law firm Leigh Day is representing 43 former inmates of a maximum security prison in Bloemfontein run by G4S in a civil damages claim.
The claim letter alleges that while in detention at Mangaung Correctional Centre the prisoners were electrocuted, forcibly injected with medications and racially abused by G4S staff.
G4S, which has been running the prison since 2001, denied the allegations and its spokesman said on Friday his company would defend itself against the claim.
"G4S insists on the highest standards of care and we not tolerate the mistreatment of prisoners," spokesman Nigel Fairbass said.
The claim letter, dated Feb. 12, 2015, is addressed to the chief executive of G4S, Ashley Almanza.
No one was available to comment at Leigh Day, which is under investigation by the Solicitors Regulatory Authority over a claim that British soldiers were involved in torture and murder in Iraq.
The allegations about Mangaung first surfaced in 2013 when the Wits Justice Project, part of the journalism department of the University of Witwatersrand said it had collected evidence of abuse from 30 warders and other sources.
The South African government took over the facility and returned it to G4S last year, saying it was satisfied the issue was resolved.
Mangaung, which houses 3,000 people, is one of only two South African prisons that are privately run. The government decided in 2010 against further public/private partnerships in prison management. ($1 = 0.6497 pounds) (Reporting by Tiisetso Motsoeneng and Mfuneko Toyana; Editing by Ruth Pitchford)