An estimated 600 buildings in England have cladding similar to that used at the Grenfell Tower block where a devastating blaze killed at least 79 people, a spokeswoman for Prime Minister Theresa May said on Thursday.

"The estimate provided to us by councils is that there are approximately 600 high rise buildings with similar cladding," the spokeswoman said.

"We are obviously in touch with all the local authorities to encourage them to urgently send us the samples and then we will carry out the checks that we need," she said.

She added that cladding on three buildings has so far tested positive as combustible. The estimate does not include buildings in Scotland, Wales and Northern Ireland.