The whole system of building regulation in the UK is “not fit for purpose”, a damning independent report in the wake of the Grenfell Tower fire has found.

Confusing rules and a lack of enforcement means construction companies are able to abuse the system, according to interim findings of the review, chaired by Dame Judith Hackitt.

The former health and safety chief has been assessing the adequacy of current guidelines in the wake of the disaster that killed 71 people.

“As the review has progressed, it has become clear that the whole system of regulation, covering what is written down and the way in which it is enacted in practice, is not fit for purpose, leaving room for those who want to take shortcuts to do so,” Dame Judith said in the report.

Buildings were not being built to specification, she said, blaming both “competence” issues and poor materials.

“What is initially designed is not what is being built, and quality assurance of materials and people is seriously lacking,” she said.

“I have been shocked by some of the practices I have heard about.”

A “cultural and behavioural change” was needed across the whole sector, she said, adding: “The mindset of doing things as cheaply as possible and passing on responsibility for problems and shortcomings to others must stop.”

Architects and senior firefighters have condemned Grenfell Tower’s single-staircase design and a lack of sprinklers in the building following the fire.

Combustible plastic foam insulation and cut-price aluminium panels with a polyethylene core fitted to the block have also been blamed for the rapid spread of the fire.

In the 10 weeks after the disaster, combustibility tests ordered by Theresa May revealed 262 high-rise residential buildings across the country were clad in the same or similar panels.

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Thousands of people are believed to still be living in buildings covered in the material, with landlords reportedly waiting to find out how the regulations are changed before they replace the panels.

The interim report urges building owners to press on with moderations improving fire safety, saying they should use materials already found to be safe.

Dame Judith told BBC Radio 4’s Today programme she “hadn’t looked at the detail” of exactly what measures – such as fire sprinklers – should be taken.

These points will be examined in the next phase of the review, which hopes to put together a new regulatory system and improve safety standards.

Regulators will now be brought together with the construction industry, councils and the Government to discuss change as part of the review’s second stage in the new year.

The Prime Minister’s official spokesman told a Westminster briefing: “Public safety is, of course, paramount, which is why following the Grenfell tragedy we commissioned this report and asked for the independent review of building regulations and safety.

“I think we would view the report as an important milestone ahead of the full report that’s due back in the spring.

Choir sings at Grenfell memorial

“As we have said, we are determined to make sure that we learn the lessons from the fire and from the inquiries that are taking place.”

He added that about 1,250 buildings have been checked for dangerous material and measures put in place when necessary.

“My understanding is Dame Judith herself was clear that her findings shouldn’t be interpreted as meaning that buildings are unsafe,” he said.

Labour‘s Shadow Housing Secretary, John Healey, welcomed the report but said the Government must not wait for the review to finish before improving fire safety measures.

“Rather than waiting for the final report of this inquiry, ministers should start acting on existing recommendations immediately and incorporate recommendations from Dame Judith Hackitt when her inquiry is completed,” he said.