Government plans to turn post-Grenfell fire safety guidance into law have been strongly criticised by a leading voice in the construction industry.

David Jones, president of the Institute of Construction Management, says the guidance for multi-storey residential buildings is “loose”, “spineless” and “open to interpretation”.

He argues it permits too many “tolerable” risks – for example, allowing flammable materials in window systems and between floors to remain even if they could let fire spread.

“It’s allowing developers to game the system,” the veteran of more than 50 years says, adding that making it law would be an “absolute abomination”.

Mr Jones is the first senior building industry leader to publicly criticise the plans, which are currently out for consultation.

The government says the guidelines are a proportionate approach to dealing with the flammable cladding crisis.

Ministers insist making them law will bring clarity and certainty to the process of deciding which fire safety defects need addressing.

Cladding campaigners say the word “tolerable” appears dozens of times in the guidelines, which are known in the industry as PAS 9980.

Combustible materials are allowed to remain in place if risks are assessed to be “tolerable” – meaning in a standard fire test a blaze does not spread beyond one floor within 15 minutes or two floors within 30 minutes.

Mr Jones argues that in the guidance, engineers are not explicitly required to present fire test safety data for these materials, making assessments subjective and open to interpretation.

He believes the lack of a ban on materials with “limited combustibility” is “another gaming of the system. It’s a fuel, it just burns a little bit slower.”

Part of the government’s motivation for tolerating certain risks is to avoid delays caused by disagreements about how much work is needed to make buildings constructed with cladding safe.

Progress has been slow in the eight years since the Grenfell tragedy.

Ministry of Housing statistics for December show around 475 of the more than 5,500 blocks so far identified as unsafe have been completely fixed and certified as safe in the last 12 months.

Cladding has been replaced in 35% of those dangerous blocks since Grenfell – including nearly all of the tallest buildings with the same type of cladding as Grenfell Tower.

Residents’ representatives fear that any flammable materials left in place can lead to a lower fire safety rating – even after repairs. In turn, this could result in permanently higher building insurance premiums.

In a statement, the government said it was up to the insurance industry to bring premiums down once buildings are certified as safe.

The insurance industry says if flammable materials remain, it will price the risk accordingly.

Mr Jones also criticises the fact the guidelines only deal with the exterior facades of buildings – covering cladding and insulation issues.

Fire safety inspections since Grenfell have revealed many tower blocks also have significant internal fire safety defects.

The government has robustly rejected Mr Jones’s criticisms.

It adds the new law will prevent what it describes as unnecessary work and disturbance for residents.

A consultation on the guidance becoming law ends on 31 December, with legislation planned in 2026.