The London Fire Brigade was closely consulted over the refurbishment of Grenfell Tower that included the installation of flammable cladding, the BBC has learned.
Documents seen by the BBC say there was “close liaison” between the fire brigade and the Kensington and Chelsea Tenant Management Organisation (TMO).
Firefighters were shown the “fire safety features of the building”.
A fire brigade spokesman said it did not “sign off” the refurbishment.
The fire brigade’s role in the refurbishment, which was completed in July 2016, would be covered by the public inquiry into the disaster, he said.
Police believe at least 80 people died when the tower was engulfed in fire on 14 June.
The fire started in a fridge-freezer, but the cladding and insulation surrounding the building following a refurbishment has also come under scrutiny, with experts saying a more fire-resistant type could have been used.
Robert Atkinson, the leader of the Labour opposition group on Kensington and Chelsea Council, said he was “completely gobsmacked” by the revelation of the brigade’s involvement in the refurbishment, adding: “I find this absolutely extraordinary and potentially very important.
“I really think we now need to make sure that the role of the fire people before the fire is looked into, and I hope that the judge and the inquiry will look at that very carefully.”
Chaired by retired judge Sir Martin Moore-Bick, it will cover the design, construction and refurbishment of Grenfell Tower as well as the response of the London Fire Brigade.
Two building experts also called for the public inquiry to investigate the role of the fire brigade in the refurbishment of Grenfell Tower.
Geoff Wilkinson, a fire expert and building inspector, told the BBC: “What I find slightly bizarre is the fact that the fire has occurred in the way it has, given the fact that the Tenant Management Organisation seem to have taken a fairly responsible approach in involving the fire service in that process.”
Paul Follows, a consulting structural engineer, said he found the revelation “quite shocking” bearing in mind the lessons learned about previous tower block fires that involved types of external cladding.
He told the BBC it was important the inquiry examined the role of the London Fire Brigade, adding: “It would be very very important, I believe, in a wide-ranging inquiry, to ask all of these questions and a lot more of the fire brigade, what they were asked, what information they were given.”
Documents seen by the BBC show “close liaison” between the Tenant Management Organisation and the London Fire Brigade “throughout the duration of the project”.
One TMO document revealed how, at the conclusion of the project, operational firefighters from the local fire station had attended an onsite briefing “where the contractor demonstrated the fire safety features of the building”.
The BBC has learned that the fire brigade was invited to liaise over the refurbishment following a fire at another of the TMO’s tower blocks in North Kensington in October 2015.
Firefighters had to rescue about 50 people from Adair Tower, in Appleford Road, after a blaze broke out in a third-floor flat. Sixteen people received hospital treatment.
Following the blaze, the fire brigade issued a series of enforcement notices that required the Tenant Management Organisation to undertake a number of fire safety improvements at Adair Tower and a second block nearby, Hazelwood Tower.
The TMO declined to comment.
The London Fire Brigade (LFB) said it did not “sign off” the refurbishment – adding that its legal powers limit the service to act only on “internal fire safety problems such as compromised fire doors and combustible materials on staircases”.
A spokesman said: “While firefighters regularly visit local buildings to familiarise themselves with the layout and the firefighting equipment such as hydrants, this is not the same as making a detailed inspection of a building refurbishment especially when many of the changes would sit outside of our powers.”
He added he could not confirm the exact contact the LFB had with the TMO regarding Grenfell Tower because the public inquiry had begun.