The Suffolk company that supplied some cladding material for the refurbishment of Grenfell Tower has been branded "dishonest" in the report on the tragedy.

Celotex, of Hadleigh, was the manufacturer of the majority of the insulation boards used in the refurbishment.

The inquiry’s final report concluded that it had “embarked on a dishonest scheme to mislead its customers and the wider market” in an attempt to break into a market.

Sir Martin Moore-Bick presents his report into the Grenfell tragedy.Sir Martin Moore-Bick presents his report into the Grenfell tragedy. (Image: Grenfell Tower Inquiry/PA Wire)

Inquiry chairman Sir Martin Moore-Bick said: “One very significant reason why Grenfell Tower came to be clad in combustible materials was systematic dishonesty on the part of those who made and sold the rainscreen cladding panels and insulation products.”

Firms had “engaged in deliberate and sustained strategies to manipulate the testing processes, misrepresent test data and mislead the market”, the report said.

And there was a warning to the companies involved from the Prime Minister.

Sir Keir Starmer said the government would write to all companies found by the Grenfell Inquiry to be part of the “horrific failings” at the west London tower block “as the first step to stopping them being awarded government contracts”.

The Prime Minister addressed the Commons after the publication of the report.The Prime Minister addressed the Commons after the publication of the report. (Image: House of Commons/UK Parliament/PA Wire)

Sir Keir told the Commons on Wednesday: “It is imperative that there is full accountability, including through the criminal justice process, and that this happens as swiftly as possible.

“So I can tell the House today that this Government will write to all companies found by the inquiry to be part of these horrific failings as the first step to stopping them being awarded Government contracts.

“And we will of course, support the Metropolitan Police and the prosecutors as they complete their investigations."

Celotex Ltd was based at Hadleigh.Celotex Ltd was based at Hadleigh. (Image: Newsquest)

The report said the Celotex Rs5000 was one of the insulation components used in the Grenfell Tower rainscreen cladding system and its TB4000 insulation was used to fill gaps in the window surrounds during the refurbishment of the tower.

In 2014 Celotex tested “with the complicity of BRE (Building Research Establishment)” a system incorporating RS5000 which contained “two sets of fire-resistant magnesium oxide boards placed in critical positions to ensure that it passed”.

A test report “omitted any reference to the magnesium oxide boards, thereby rendering it materially incomplete and misleading” and the product was marketed as the first to meet that test and as “acceptable for use in buildings above 18 metres in height”.

But the report said the test Celotex relied on to support this claim “had been manipulated as we have described above, a fact that Celotex did not disclose in its marketing literature.”

The Grenfell report runs to 1,700 pages in seven volumes.The Grenfell report runs to 1,700 pages in seven volumes. (Image: PA)

A statement released by Celotex after the publication of the report said: "The publication of the Grenfell Tower Inquiry Report marks the conclusion of the Inquiry’s work and we are considering its contents with care. 

"Our business’ response to what happened started immediately after the fire in June 2017.

"We conducted our own review to interrogate the circumstances in which the RS5000 product had been tested, launched and marketed.  

"This review was a significant and thorough undertaking, and the results of that work were disclosed promptly and proactively to relevant stakeholders, including the Grenfell Tower Inquiry.

"Independent testing commissioned following the review demonstrated that the cladding system described in the Celotex RS5000 marketing literature met the relevant safety criteria.

"That system was substantially different to that used at Grenfell Tower.  Decisions about design, construction and the selection of materials for the Tower were made by construction industry professionals.

"Since the fire, we reviewed and improved process controls, quality management and the approach to marketing within the Celotex business to meet industry best practice.

"Celotex Limited continues to cooperate fully with all official investigations into the Grenfell Tower fire. We reiterate our sympathies to everyone affected by the fire."

The Celotex site at Hadleigh was sold last year by the company's French owners to Essex-based Soprema UK.

That now manufactures products under the 'Celotex by Soprema' branding - but there is no direct link with Celotex UK which is the company under the spotlight in the Grenfell Report.