The government has not analysed how much households will save on their energy bills despite its £100 claim

The government has made no estimate of how much its proposed energy price cap could save households, despite Theresa May’s claim that it would cut bills by up to £100 a year.

The prime minister has vowed to bring an “end to rip-off energy prices once and for all”.

The plan to set a maximum price for gas and electricity would apply to about 11 million households that are on expensive standard tariffs and are not already protected by existing price caps. Ministers say that the cap is necessary after the competition watchdog found that most Britons were paying too much, amid inefficiency and excessive profits at leading suppliers.

An official impact assessment being published today reveals that the government has not analysed how much