The IHT liability has risen to £157,000 and £106,000 respectively for estates with a property based in London and the South East, on average, because of surging house prices which have been greatest in those regions over the 14-year period, research by interactive investor shows.

Instead of being uprated with inflation, the IHT threshold has remained at £325,000 since 2009 and will remain frozen at that level until at least 2028.

Meanwhile, growth in house prices, investments and savings (which are among the key assets factor when calculating IHT liability) over the 14-year period means that even modest estates could be subject to IHT.