The chair of the Grenfell Inquiry revealed this morning that some of the people involved with the 2016 refurbishment of the tower have asked for a form of immunity before they give evidence. Employees and ex-employees from Rydon, Harley Facades, Studio E, Osborne Berry Installations, independent cladding designer Kevin Lamb and the Kensington and Chelsea TMO (Tenant Management Organisation) are among those who have made the request ahead of giving evidence about material choices and designs.

Sir Martin Moore-Bick told the inquiry he had been notified by a number of people due to give evidence about the design next week that they might refuse to answer some questions. In legal terms they will claim “privilege against self-incrimination”, which means they cannot be compelled to answer any question that could lead to prosecution. Moore-Bick said he was “surprised” at their stance.

He said: “This development has caused me a little surprise because hitherto there has been the fullest cooperation with the inquiry, both of giving written statements and in the provision of documents, and no one, so far, has sought to avoid doing that or to avoid answering any of our questions on those grounds.”

Witnesses have asked the chair to make a request to the attorney general that anything they say at the inquiry will not be used against them in any prosecution that might arise. With witnesses due to face questioning from next week, Moore-Bick said he would deal with their application tomorrow afternoon.

Survivors and those bereaved by the fire, which killed 72 people on 14 June 2017, who were present at the hearing this morning expressed frustration at what one called “legal tactics”.

Witnesses said they have made the request on the basis that there is an ongoing police investigation into the fire that has a very wide scope and considers potential offences, ranging from regulatory breaches to gross negligence manslaughter. With the witnesses not being given prior notice of what they will be asked by the inquiry's lawyer, or what evidence will be presented, their own lawyers have argued that they are entitled to exercise their privilege to not provide self-incriminating testimony. If the immunity is not granted, then the chair will have to remind witnesses of their right not to answer every time they are asked a question.

“All of this is likely to have the undesired effect of seriously impeding the inquiry’s work,” a joint letter from the witnesses’s lawyers has said.

The inquiry continues.