Families could face a new “extra death tax” as part of Rachel Reeves’s plans to target high-value properties through a form of mansion tax.

The Chancellor is reportedly considering a £600million surcharge on hundreds of higher-value homes, using the existing council tax system to revalue 2.4 million properties in bands F, G, and H. This translates to approximately one in 10 homes in England. But to avoid forcing “asset-rich, cash-poor” households to sell up, such as pensioners, Ms Reeves is expected to allow homeowners to defer the charge until they move or after they die, the Telegraph reports.

This means some families could face an additional bill on top of the 40% inheritance tax already levied on some estates.

Conservative leader Kemi Badenoch branded the measure an “unjustified raid on pensioners”.

Sir Mel Stride said it amounted to “a new death tax by the back door”, while Reform UK’s Richard Tice accused the Chancellor of breaking her promise not to raise taxes, calling the plan “cynical and cruel”.

The Treasury may also apply interest to deferred payments to prevent inflation from eroding future revenue, which is an approach recommended by the Institute for Fiscal Studies (IFS).

Stuart Adam of the IFS said allowing deferral “until sale of the property, death, or up to 10 years” makes sense, but warned it must come “with interest – like a commercial loan”.

The reforms are expected to affect many of the 1.3 million families in Band F homes, who could face annual bills of several hundred pounds, while owners of the most valuable properties may pay thousands more.

After dropping income tax rises, the Chancellor is thought to be preparing a series of smaller tax measures and an extension of frozen thresholds.

Ms Reeves will unveil the Autumn Budget on November 26.