Party says chair of government fire safety panel had approved cladding similar to that which spread Grenfell fire

The government’s chief fire safety adviser approved as safe for use cladding similar to that which spread the deadly Grenfell Tower fire, according to a certificate unearthed by Labour.

Sir Ken Knight, who was appointed as the independent expert advisory panel on making buildings safe after 72 people died at Grenfell, signed a safety certificate in 2014 for a combustible aluminium cladding panel with polyethylene core that said it could be used in “multi-storey” buildings.

Labour said this demonstrated that Theresa May and other ministers were wrong when they said in the aftermath of the inferno that this polyethylene cladding had been banned in the UK for multi-storey buildings. It “called into question the government’s entire fire safety system,” the party said.

Steve Reed, Labour’s civil society spokesman, wrote to the housing secretary, Sajid Javid, to say: “Ministers repeated claims that the kind of cladding used on Grenfell Tower was not permitted have been exposed as false by the very man who chairs your fire safety panel.”

The certificate Knight signed said the panels could be used in multi-storey residential buildings in accordance with building regulations guidance. But since June, Knight’s expert panel has claimed that such a material would not meet regulations, which require that the cladding and insulation used are of limited combustibility.

The Ministry of Housing, Communities and Local Government (MHCLG) said: “Steve Reed MP is wrong. The certificate he referred to does not approve cladding with a polyethylene core for use on high-rise buildings.”

But Reed says the certificate shows Knight signed it, that it covered multi-storey blocks, and refers to a polyethylene core. “The government are desperate to avoid admitting their mistake because it will make them liable in law for replacing this kind of cladding where it exists.”

Steve Reed (@SteveReedMP) .@mhclg say I'm wrong about Govt adviser approving Grenfell-style flammable cladding. Here's his signature on the certificate, the line about multi-storey buildings, and the type of cladding @insidehousing pic.twitter.com/Z9RjXnJNDz

In 2014 Knight held a role as chairman of the impartiality committee for Warrington Certification, a private fire testing company. He signed a certificate that stated a cladding product called Larson, made by Alucoil, had a “Class 0” rating after it was tested for fire propagation and surface spread of flames. This is the lowest level of fire spread.

The certificate states that “a material with a fire performance classification of Class 0 may be used in the following areas within a building” – and listed the outsides of multi-storey buildings including homes, care homes, offices, shops and recreational buildings.

However days after Knight was appointed to lead the expert panel on fire safety, the government published a warning that a Class 0 rating for the surface of ACM panels “does not cover the limited combustibility requirement for the core or filler material within an ACM panel”.

Knight’s panel then issued revised advice stating that building owners replacing cladding must ensure that cladding and insulation used are of limited combustibility. The Alucoil material is certified as class E under the European EN 13501-1 test which means it is combustible, and its Spanish manufacturer advises against its use in high-rise buildings.

It has previously been reported that Knight said his role for Warrington Certification was to sign off on the impartiality of the certification scheme as a whole and not to certify individual products. However his signature is on every page of the Alucoil document.

Knight was previously the London fire commissioner and the government’s chief fire and rescue adviser. He has previously stressed that he resigned his position chairing the impartiality panel of Warrington Certification when he took the chairmanship of the government advisory panel.

Fire safety campaigners, who believe that the government should concede that the building regulations did allow such products to be used before Grenfell, have seized on the document as evidence that Knight’s position has shifted. They believe that the government rather than building owners and residents should be held responsible for the cost of replacing what is now seen as dangerous cladding.

Stephen McKenzie, an independent fire and emergency planning consultant, said the test Knight signed off was “defective and lulled people into a false sense of security”.

A spokesman for the MHCLG said: “Sir Ken Knight’s role was to sign off the impartiality of the certification scheme as a whole, and not approving specific cladding systems.”

Knight said: “The certificate in question does not approve cladding with a polyethylene core for use on high-rise buildings. To state otherwise is categorically incorrect and misleading.”