As many as 20,000 farmers will demonstrate outside Parliament on Tuesday, including Jeremy Clarkson and Kaleb Cooper, the stars of Clarkson’s Farm.

While the Treasury insisted the change would only affect a small number of farms, critics warned it could harm the UK’s food security.

Sir Keir Starmer, who is in Brazil for the G20 summit with world leaders, stood firm on the decision, stressing that the budget included a record £5 billion commitment for agriculture.

Speaking to reporters on a flight to Rio de Janeiro, he said: “Clearly there is an issue around inheritance tax and I understand that concern.

“But for a typical case, that of parents owning a farm which they wish to pass on to one of their children, when you have taken into account not only the exemption for the agricultural goods themselves, but also the he exemption for joint spouse, then parent to child, is £3 million before any inheritance tax is payable.

“That is why I am absolutely convinced that the vast majority of farms and farmers will not be affected by this situation.”