Cells unfit for habitation, blocked toilets and a failure to maintain basic facilities – these are among the discoveries made at prisons serviced by failed company Carillion.

The contracting giant was responsible for managing facilities at around half of the UK's prisons, including Norwich, Wayland and Bure in Norfolk, Hollesley Bay and Highpoint in Suffolk, Whitemoor in Cambridgeshire, and Chelmsford.

But a damning assessment of its work for the Ministry of Justice has been released by the UK's Independent Monitoring Boards, responsible for inspecting prisons, following the company's collapse on Monday under a mountain of debt and a £590m pension deficit.

IMB national chair Dame Anne Owers said concerns about the 'poor condition' of prison environments often fell at the door of Carillion's facilities management arm.

'Boards have pointed out, in their annual reports, that some of these defects have seriously affected the health and safety of prisoners and the security of establishments. They include failure to maintain kitchen equipment, showers and boilers, cells that are unfit for habitation, and unrepaired external lights and windows,' she said.

The IMB said it will continue to monitor these services and report on their impact.

A 2016 IMB report for Hollesley Bay prison said Carillion 'frequently relegates minor repairs to 'low priority' status which incurs long delays' for work which many inmates are skilled in, adding: 'The board considers it wasteful and frustrating that these rich resources cannot handle more of the routine maintenance.'

Similar reports of a struggle to handle on-site maintenance efficiently – leading to delays for even simple repairs such as unblocking toilets and fixing lights – came from Norwich and Chelmsford prisons.

A report for 2016 for Highpoint prison noted 'no improvement' in maintenance services provided by Carillion from previous inspections and a lack of support for prison management. While the company's on-site team 'attempt to meet the requirements of the contract, external constraints and management militate against this', the report said. This, along with other concerns raised by prison staff, elicited a ministerial response.

The Insolvency Service, which is managing Carillion's liquidation and investigating the causes of its failure, said it would not comment on specific allegations.