The Australian company that operated the Bibby Stockholm asylum barge has admitted overcharging by £118million - £40million more than originally estimated.
Corporate Travel Management (CTM) said 'erroneous billing' of UK clients, including the Home Office, was discovered as part of a 'forensic' probe by accountants KPMG.
It had previously discovered a £77.6million accounting error, but CTM now updated this to £118million in an announcement to the Australian Securities Exchange.
The company outlined how it was asked to 'rapidly source accommodation for thousands of people' in 2021.
It subsequently 'secured in excess of 1.4 million nights of accommodation at in excess of 60 hotels across the United Kingdom', the firm added.
But, by late 2022, it had 'identified differences of £54.6 million between the amounts charged to, and paid by the customer and the amounts paid to hotels'.
CTM was previously revealed to have won public sector contracts worth £3.9billion over the past 10 years, including a £1.6billion contract for the Bibby Stockholm barge.
The vessel was moored in Portland, Dorset, with plans for it to house hundreds of migrants as the previous Tory government attempted to cut the bill for hotel accommodation for asylum seekers.
The Australian company that operated the Bibby Stockholm asylum barge has admitted overcharging by £118million - £40million more than originally estimated
After winning power in July 2024, Labour scrapped the plans to house people on the barge in an overhaul of the asylum system.
The Home Office said an internal investigation is still taking place into CTM contracts.
A spokesperson said: 'An internal investigation is continuing into this overspend.
'We have already recouped over £70million so far from asylum accommodation contracts which were not delivering good value for money.
'Our changes have strengthened contract management and saved £700million in hotel costs alone, as the Government works towards its commitment to close every asylum hotel.'
CTM's shareshave been suspended on the Australian Securities Exchange since August last year.
Ewen Crouch, the firm's chairman, said: 'The ongoing trading suspension and its impact on shareholders is deeply disappointing and a matter of serious concern for the board.
'We sincerely apologise to our shareholders and to affected clients in the UK for the circumstances that led to this situation.
'The length of the suspension reflects the Board's determination to fully investigate the issues identified in the UK and to address them decisively and completely.
'Today's announcement marks an important step forward, and we continue to work constructively to finalise our work to allow the auditors to complete their procedures.'