The liquidation of Carillion will cost UK taxpayers an estimated £148m, the National Audit Office (NAO) has said, excluding around £2.6bn pension liabilities and losses by the firm’s non-government creditors.

The NAO has published its investigation into the Government’s handling of the collapse of the infrastructure and outsourcing giant.

The Government has largely escaped criticism in the report, although the NAO said it needs to ‘do better’ at understanding the financial health of its top suppliers and avoid creating relationships with those that are already weakened.

The Cabinet Office's estimated £148m bill for the insolvency is subject to a range of uncertainties and it could take years to establish the final cost, auditors said. This would be covered by the £150m the Cabinet Office has already provided.

The NAO added that Carillion’s non-government creditors ‘are unlikely to recover much of their investments’, and the company’s extensive pension liabilities, totalling £2.6bn as of June 2017, will need to be compensated through the Pension Protection Fund.

Amyas Morse, the head of the NAO, said: ‘When a company becomes a strategic supplier, dependencies are created beyond the scope of specific contracts.

‘Doing a thorough job of protecting the public interest means that government needs to understand the financial health and sustainability of its major suppliers, and avoid creating relationships with those which are already weakened. Government has further to go in developing in this direction.’

The investigation has identified that the Cabinet Office began planning for the possible failure of Carillion shortly after the company posted its first profit warning in July 2017. It states: ‘The scale of the profit warning came as a surprise to the Government, as it contradicted market expectations and information and commentary that had been provided by Carillion.’

A longer version of this article first appears on Transport Network