Robbie Moore, the Conservative shadow agriculture minister, told the Telegraph: “Steve Reed doesn’t seem to have had much interest in agriculture before he became secretary of state, let alone now.

“The Labor family your farmx will have such a negative impact on the landscape that he now even advises farmers how to avoid it. These damaging tax rises will destroy farmers’ livelihoods, raise prices for consumers and put the UK’s food security at risk. The conservatives would overthrow them.

Labor’s decision to end the decades-old practice of letting farmers pass on their estates without paying inheritance tax proved to be one of the most controversial aspects of the budget.

Inheritances worth more than £1million will be subject to an effective rate of inheritance tax of 20 per cent, although some farmers can be spared on estates worth up to £3 million if they pool tax-free allowances.

Labor argued that only a fraction of farms would be affected and that the policy closed a loophole that allows tax evaders to buy farmland.

But critics, including the thousands of farmers who came down to Westminster on Tuesday to protest the change, said real farming families would be forced out of business.