Carillion is one of the worst disasters to hit British business in years. Unlike bank collapses, this involves hundreds of sub-contracting firms who have hired workers from Carillion who could now face bankruptcy and winter redundancy.

It is clear that government taken as a whole – the Treasury, Transport, Education, and Justice departments – failed to exercise sufficient supervision over the firm and its myriad operations. Right across national and local government, officials were awarding contracts to Carillion and its sub-contractors until just a few days ago.

But ministers and their senior officials are now diverting so many resources to Brexit that they have no time or civil servants to oversee other key areas of government activity.

Two new ministries have had to be set up – the Department for Exiting the EU (Dexeu) and the International Trade Department (DIT). Hundreds of civil servants have been transferred from other departments to these two Brexit departments, set up to allow ultra-eurosceptics like David Davis and Liam Fox to be brought back from the political graveyard which previous Tory leaders had sensibly left them, given their record of poor judgement, laziness, and eccentricity.

Dexeu has been so useless that the chief Brexit civil servant, Olly Robbins, a Whitehall high flyer, has transferred back to the Cabinet Office and now reports directly to the cabinet secretary, Jeremy Heywood, and the prime minister.

Davis – who is 70 this year, close to the average age of Tory members which is 71 – is now merely decorative. His blustering bonhomie and ad hominem attacks on Michel Barnier have made zero impression on the EU27 and the team in Brussels responsible for negotiating Brexit.

The Treasury, which normally exercises the tightest control on all aspects of government spending and does due diligence on firms awarded public contracts, has had to devote immense resources to Brexit, preparing hundreds of papers and holding endless meetings with the City and service industry firms which will be hit the hardest if the UK leaves the single market and customs union.

Top-rank British civil servants are hard-working and often very clever. But Brexit has caused so much disruption that normal work, like supervising firms such as Carillion, has had to be put on hold to focus on Brexit. The quality of work has not been impressive as the publication of the so-called “impact assessment” reports, which were empty of substance, showed.

But even a report full of pointless verbiage still takes time to produce, and other government work has to be left undone. Brexit is like a parasite sucking the life juices out of government. There are many causes for the Carillion disaster but the way Brexit has taken over normal government work did not help.

Denis MacShane was a Labour MP for 18 years and is a former Minister for Europe. He is a Senior Advisor at Avisa Partners.