The Grenfell Tower inquiry has hired KPMG as its adviser despite the accountancy firm earning millions of pounds auditing three of the main players being investigated over the tragic blaze and its aftermath.

KPMG has lucrative and long-standing relationships as auditor to Rydon — the main contractor in charge of the refurbishment widely blamed for the fire’s spread — Celotex, the maker of the insulation which police said failed safety tests, and the much-criticised Royal Borough of Kensington and Chelsea.

News that the inquiry is paying a firm so closely linked to the organisations under scrutiny is bound to anger survivors and victims’ families. They have already voiced concerns that the investigation is lacking in diverse voices.

KPMG was hired by the Cabinet Office to help plan the inquiry and monitor its progress.

The three-month, £200,000 contract (recently extended to February) was awarded in a fast-track process with no other bidders considered.

An Inquiry spokesman for said this was to save time due to the need to set up the investigation rapidly.

He said the Inquiry knew of KPMG’s connections to Rydon and the borough, but was unaware of the Celotex link until being informed by the Evening Standard.

It said it hired KPMG despite the firm’s work for the other organisations because it was “uniquely placed to offer specialised programme management, decision support and impact planning”.

KPMG has earned nearly £1 million in fees since taking over as auditor of under-fire Royal Borough of Kensington and Chelsea in 2012.

The borough is being questioned over perceived failings in helping survivors in the immediate aftermath of the fire.

The accountant has made £3.5 million since 2007 offering audit, tax and other services to Rydon.

It has made a further £1 million over the same period as auditor to Saint-Gobain Construction Products UK, owner of insulation maker Celotex.

Over the past decade, SGCP’s French parent company, Saint-Gobain, paid KPMG’s global partnership £109.2 million in audit and other advisory fees.

KPMG said its role in the inquiry was “purely operational”, advising on project management, and it had “no role advising on the substance of the inquiry”.