The ex-Labour PM says Sir Keir Starmer's government is in the "wrong position" ahead of the next election.
Temperatures soared to 35.1C in Kew Gardens, south-west London, according to provisional figures.
A household using a typical amount of gas and electricity is forecast to pay about £200 more a year.
The spy agency's head will set out threats facing the UK and the measures she believes need to be taken to confront them on Wednesday.
Former Prime Minister Sir Tony Blair's essay criticising Labour and the ongoing heatwave lead the papers.