The Guardian reports that tenants in the UK’s draughtiest homes risk paying £1bn extra in energy bills because of a government loophole letting landlords off the hook, a charity has warned.

Landlords will be banned from letting poorly insulated homes from next April under new regulations designed to protect vulnerable tenants and cut carbon emissions.

But campaigners argue that exemptions, which landlords were able to apply for from Sunday, will mean many homes are not upgraded.

If all the landlords of the 300,000 properties affected apply successfully for exemptions, tenants would collectively pay £1bn extra for energy over the next five years, said climate change charity 10:10.

The group said the regulations were “toothless” while the loophole existed, and made a mockery of Conservative election pledges to keep a lid on energy bills.

Liberal Democrat MP Ed Davey, the former energy secretary who set the regulations in train, said:

“The government must urgently confirm that new private green deal finance options will prevent landlords from wriggling out of their responsibilities.

“Given these regulations will save some low income tenants over £1,000 a year on their energy bills – far more than any energy price cap ever might – as well as cutting carbon emissions, it would be outrageous if the Conservatives gave landlords any loophole.”