Undertaken by the Institute for Public Policy Research, it claims the chancellor could raise £147m a year through the special tax rate.
Downing Street distanced itself from the report but opposition parties claimed Labour had ‘let the cat out of the bag’ and was planning a raft of tax rises if they win the next election.
The IPPR plan would see the IHT threshold remain at £263,000.
Above that, the 40% tax rate would be replaced by 22% marginal for up to £288,000, increasing to 40% for amounts up to £763,000.
The 50% rate would only apply to estates over £763,000.
Drastically fewer offices for HMRC in the hope to reduce their running costs
Tayabali Tomlin and d&t directors launch £20 a month TaxGo service, aiming to be the 'biggest UK firm' by client numbers
Companies must report on their complex financial structures including offshore accounts and notify HMRC
An examination by the Public Accounts Committee (PAC) has revealed serious concerns relating to HMRC’s plans