The insulation material used in the refurbishment of Grenfell Tower "will burn if exposed to a fire of sufficient heat and intensity", according to its manufacturer.

Celotex confirmed that it supplied its RS5000 insulation for the £8.6 million renovation of the London tower block, where at least 12 people died and scores were injured.

It came after experts warned that the process of adding rain-proof cladding to tower blocks could create an additional fire risk.

Arnold Tarling, a chartered surveyor and fire expert with property firm Hindwoods, said that the process can have the effect of creating a "wind tunnel and also traps any burning material between the rain cladding and the building".

He said it can create a 25mm-30mm cavity between the surface and the insulation behind it, adding: "So had it been insulated per se, the insulation could fall off and fall away from the building, but this is all contained inside."

He said not all insulation used in the process is the more expensive non-flammable type.

"So basically you have got a cavity with a fire spreading behind it."

RS5000, according to Celotex's website, has a Class 0 rating under UK building regulations, meaning it has the highest rating for preventing the spread of flames and prevents the spread of heat.

However, its "health and safety datasheet" notes: "The products will burn if exposed to a fire of sufficient heat and intensity.

"As with all organic materials, toxic gases will be released with combustion."

Design specifications seen by the Press Association suggest the renovation work carried out at Grenfell Tower included plans for a 50mm "ventilated cavity" next to 150mm of Celotex FR5000 insulation, which also has a Class 0 rating.

A Celotex spokeswoman added: "If required, we will assist with enquiries from the relevant authorities at the appropriate time."

Angus Law, of the BRE Centre for Fire Safety Engineering at the University of Edinburgh, said: "Early media reports suggest that this event has similarities with other fires that have occurred recently around the world."

He added: "The UK's regulatory framework for tall residential buildings is intended to prevent the spread of fire between floors and between apartments.

"If spread of fire does occur, as has happened at Grenfell Tower, the consequences are often catastrophic."

Construction firm Rydon, which carried out the refurbishment, installing cladding and new windows among other work, said it "met all required building control, fire regulation, and health and safety standards".

A document submitted in a 2014 planning application linked to the work said that the exterior panels were made from "Reynobond/Reynolux".

These panels, made by US firm Arconic, consist of Reynolux coated aluminium sheets over a Reynobond polyethylene core.

The firm's website says that the sheets have the highest A1 European fire safety rating and are "incombustible".

The interior comes in two forms, one with an A2 rating that is "non-combustible" and a second with a lesser B rating that is described on the website as "fire retardant" and "non-flammable, which prevents fires from spreading".

It is not clear which was used at Grenfell Tower.

In July last year, the 75-storey Sulafa Tower in Dubai Marina went up in flames, following a number of similar fires in the Middle East, including one at the 63-storey The Address Downtown Dubai on New Year's Eve 2015.

James Lane, head of fire engineering at BB7, told IFSEC Global last July: "Another high-rise apartment block is apparently victim to the poor fire properties of its external cladding.

"Any building constructed before the 2013 change in the local fire codes will be at risk from this kind of rapid and extensive fire spread unless major work is undertaken in the region to replace combustible insulation core cladding panels with a suitable alternative."

The planning application was approved by the Royal Borough of Kensington and Chelsea after planning officers recommended it be passed, subject to conditions.

As well as improving the block for residents, the officers' report recommended rules be put in place regarding the materials used, noting: "Due to its height the tower is visible from the adjacent Avondale Conservation Area to the south and the Ladbroke Conservation Area to the east.

"The changes to the existing tower will improve its appearance especially when viewed from the surrounding area."

In May 2016, after the work was completed, Kensington and Chelsea council leader Nick Paget-Brown said: "It is remarkable to see first-hand how the cladding has lifted the external appearance of the tower and how the improvements inside people's homes will make a big difference to their day-to-day lives."