The head of two G4S-run detention centres has been placed on administrative leave after a series of scandals, the Guardian has learned.

G4S is believed to have placed Ben Saunders on leave from his role in charge of Brook House and Tinsley House immigration removal centres (IRCs) after an undercover Panorama exposed abuse of detainees there. Officers were seen to mock suicidal detainees and one officer is alleged to have attempted to choke a detainee.

A G4S source at managerial level told the Guardian: “Senior managers were called to a meeting yesterday and told Saunders was put on leave”. G4S declined to comment on the report.

The news is another unfortunate milestone in a difficult period for G4S, which has faced severe criticism over its management of the two IRCs in the UK.

The Guardian revealed this week that both detention centres appeared to make larger profit margins than that agreed with the Home Office. Documents showed profits before tax upwards of 20% whereas the original contract between G4S and the Home Office showed an agreed profit margin of 6.8%

G4S said the higher figures did not reflect final profits as they did not take into account company-wide costs and overheads.

Last week, the Guardian also revealed that Saunders had been in charge of a children’s prison in 2009-10 when children were maltreated. Like the two IRCs, Medway Secure Training Centre in Kent was then run by G4S, before it gave up its children’s services division after abuse and alleged corruption were exposed by the Guardian investigation and another Panorama undercover operation.

The Home Office is under increasing pressure to strip G4S, the largest security firm in the world, of its contract to run the IRCs after the latest revelations of abuse and possible financial irregularities.

On Thursday, Peter Neden, regional president for UK and Ireland, and Jerry Petherick, managing director for custody and detention centres, gave evidence before the home affairs select committee about the Brook House scandals.

Neden told the committee chair, Labour MP Yvette Cooper, that he was not “at liberty to disclose the profits”. She replied: “The fact that some very serious allegations have been made about G4S not providing full and accurate information to the Home Office and, also, the fact that this is profit on a service in which there has now been very serious evidence of abuse and mismanagement taking place, means that actually it is not acceptable for you simply to provide no information about the profitability on these contracts.”

When Petherick was asked whether he had considered his position, he replied: “Yes. I would be an idiot not to … At the moment, my job is to be the leader. It is my job to take Brook House, and the rest of my business, through this. Of course I have looked at myself; I would be failing in my duty to everyone if I hadn’t.”

Cooper concluded: “Mr Petherick and Mr Neden, I am afraid that the answers you have given do not suggest that you have any grip on this at all.”

The Rev Nathan Ward, former duty director at Brook House and now a Church of England priest, was asked by the select committee whether he was shocked by the Panorama footage of Brook House. He replied: “I wasn’t surprised, but shocked at the level of abuse that was going on. I had been raising concerns about practice within G4S since 2001. In particular, I raised concerns to Jerry Petherick upon my resignation.”

When questioned about G4S profit margins at the IRCs, Ward said: “I have certainly seen presentations with 30% profit margins put on them.” When Cooper asked if it was plausible that G4S had deliberately given false information to the Home Office about profit margins, Ward replied “Categorically, yes.”

The shadow home secretary, Diane Abbott, told the Guardian: “It is clear from the endless list of complaints and scandals that the Home Office are aware of improper conduct among G4S staff. Yet they stand by as this company continues to employ staff who have run failed institutions. It’s high time the Home Office brought its agents to order, and if things do not improve consider a review into whether G4S should remain a service provider.”

When asked whether it was considering pulling out of its contract to run the two IRCs, G4S said: “We remain committed to running Brook House and Tinsley House immigration removal centres on behalf of the Home Office. The wellbeing of those in our care is our priority.”