Allies of Mr Burnham, who will walk through the doors of No 10 in just over a week's time, are understood to be studying a raft of proposals, which would hammer the rich.

UK families could face significantly larger tax bills under a Burnham premiership, as speculation over his potential changes

Experts have warned middle-class families, who live in relatively modest homes and not 'mansions' as the term would suggest, would be dragged into the tax.