75 high-rise blocks across 26 local authorities in the UK have failed fire safety tests since the Grenfell Tower disaster.

Checks are being carried out on hundreds of tower blocks after it was established that the cladding on the 26-storey building helped the fire, which is believed to have killed at least 79 people, to spread.

The UK's communities minister Sajid Javid told MPs that the so-called combustibility test had been failed by every building examined so far.

"The fact that all samples so far have failed underlines the value of the testing programme and the vital importance of submitting samples urgently," he said.

"I am concerned about the speed at which samples are being submitted.

"I would urge all landlords to submit their samples immediately."

Schools and hospitals will also be tested to make sure their cladding is not combustible, Downing Street said earlier.

The latest update on the number of buildings on which the flammable cladding was used came as the US supplier of the covering said it was stopping sales for high-rise buildings.

"Arconic is discontinuing global sales of Reynobond PE for use in high-rise applications," a company spokesman said.

The firm put the decision down to "issues that have arisen in the wake of the Grenfell Tower tragedy" and differences in building regulations around the world.

Labour has called for a "triple fire safety lock" to guarantee the standards of buildings.

Shadow housing secretary John Healey said such a guarantee would include materials being fit for purpose and meeting safety specifications, plus regular fire risk assessments.

Meanwhile, Westminster coroner Dr Fiona Wilcox opened and adjourned the inquests into the deaths of four people in Grenfell Tower.

The inquest heard five-year-old Isaac Paulos choked to death on fumes from the fire and had to be identified by his dental records

He lived on the 18th floor, but his body was found on the 13th. He had disappeared as his family attempted to escape the flames.

The other three victims whose inquests were opened included artist Khadija Saye, 24; her mother, Mary Ajaoi Augustus Mendy; and Mohamednur Tuccu, 44.

All three were also recorded as inhaling fumes.