- Video report by ITV News political correspondent Paul Brand
The number of high-rise tower blocks known to be a fire risk has risen to 34 as the Government revealed every single sample of cladding tested so far has failed the safety checks.
Communities Secretary Sajid Javid announced the latest rise in a statement that added "all samples so far have failed the tests".
A spokesman for the Government said they had only received a few dozen samples so far - but they were thought to be among the most concerning in terms of fire safety.
However, with some 600 tower blocks thought to be fitted with cladding, it suggests that the number of blocks at a fire risk will rise further in the coming days.
Councils have been given until Monday to submit cladding samples for tests in an urgent review after the fire at Grenfell Tower killed at least 79 people.
So far, Manchester, Camden, Plymouth, Hounslow, Portsmouth, Barnet and Brent have been named as local authorities with buildings that failed tests.
On Friday night up to 4,000 residents from 600 households on the Chalcots estate in north London were evacuated to allow "urgent fire safety works" to take place.
The tower blocks were found to have similar cladding to that used on Grenfell, and also had other fire safety failings.
Also on Friday night, a housing company declared a block of flats in Kennedy Gardens in Billingham in County Durham was covered in combustible cladding.
Mr Javid said that laboratories were "running around the clock" to carry out the safety checks and would be able to test as many as 100 samples per day.
He added: "The fact that all samples so far have failed the tests underlines the value of the testing programme we have set up."
The minister praised the "calm and stoicism" with with many residents in the Chalcots estate greeted the news they should leave their homes.
Mr Javid has said there will have to be a long-term review of safety regulations, stating: "That has to happen. In a country like ours, one of the richest countries in the world, in the 21st century, these kind of things absolutely should not be happening."
Birmingham City Council leader John Clancy called events "a national emergency" and called for Government funding to help improve safety for affected blocks.
"We think in the context of this national emergency the Government should certainly be assisting if not fully funding," he said.
He earlier said: "As each day has gone by since this crisis started, there seems to be less clarity. There is a collective national trauma at the moment and people up and down the country go to bed afraid."
On Thursday, Theresa May today urged social landlords to send samples as soon as possible, saying: "We cannot and will not ask people to live in unsafe homes."