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.
Crowe Clark Whitehill , the top 20 accountancy firm, has announced the promotion of Chris Mould to partner
The latest opinions from Accountancy Age on Making Tax Digital, and outline plans to evolve the UK's corporate governance regime
Five million taxpayers are ow using digital personal tax accounts (PTA) as part of the making tax digital strategy, HMRC said
UK-based non-doms have paid ten times more tax than the average taxpayer, raising concerns over the Brexit impact on non-dom contributions and therefore, the economy