Thousands of farmers stabbed in the back by Labour’s inheritance tax raid will unleash their fury at a mass protest on Tuesday, a farming union boss has warned.

National Farmers Union members (NFU) and Jeremy Clarkson are among the 20,000 people expected to descend on Whitehall to demonstrate against Rachel Reeves’ budget announcement last month.

The NFU is holding a mass lobby of MPs with 1,800 of its members – three times as many people as originally planned – to urge backbenchers to stand up to the Government’s plans to impose inheritance tax on farms worth more than £1 million.

And thousands more are expected to join a separate rally in Whitehall as they protest against the budget.

NFU President Tom Bradshaw is expected to tell farmers on Tuesday that he has never seen the industry “this angry, this disillusioned and this upset”.

He will add: “To launch a policy this destructive without speaking to anyone involved in farming beggars’ belief.

“And let us remember that they promised not to do this when they were wooing the rural vote. It’s not only been bungled in delivery, it’s also nothing short of a stab in the back.

“But we in this room also know that agricultural property relief and business property relief is the straw which broke the camel’s back for farming. After years of changing policy and 18 months of some of the worst weather on record, the budget has been a kick in the teeth. It is full of let-downs for our vital sector.”

Protests on Tuesday will be the largest show of anger to date over the inheritance tax changes for farming businesses, which limit the 100% relief for farms to only the first £1 million of combined agricultural and business property.

For anything above that, landowners will pay a 20% tax rate, rather than the standard 40% rate of inheritance tax applied to other land and property.

Rupert Burchett, agricultural property solicitor at legal firm Payne Hicks Beach, said: “The Government campaigned on a promise to give ‘our rural communities their future back’ and were adamant that they would not change agricultural property relief.

“These proposals directly contradict those promises. Even if you just use bare agricultural land values, 40% of farms will be affected.

“When you add on the value of farmhouses, diversified farm buildings and so on, that figure skyrockets. There is a real and understandable sense of betrayal in our rural communities.”

Environment Secretary Steve Reed met with Mr Bradshaw on Monday in an attempt to quell farmers’ anger.

The Treasury and the Department for Environment, Food and Rural Affairs (Defra) have been unable to agree how many farms will be hit.

Mr Reed defended the changes as “fair and balanced”, saying it would only affect 500 estates a year and small family farms would not be hit.

But campaigners, using an analysis of Defra figures, have insisted up to 70,000 people could be affected.

Farmer Andrew Ward said: “Our job is to put food on people’s plates and we should be planting next year’s crops. But, the march today is too important to miss.

“The Budget threatens the destruction of the farming industry as we know it and family farms and other businesses will be lost. If this happens, we can’t feed people and wildlife will also suffer. It’s that simple.

“We haven’t seen a threat to our rural way of life like this in decades. We have to make sure our voices are heard and the Government listens.”

The Daily Express has launched the Save Britain’s Family Farms crusade to demand Ms Reeves U-turns on her decision.

Tory leader Kemi Badenoch said: “The Labour government clearly doesn’t understand, or care about rural communities, and now families are having to sell their farms, with knowledge that has been handed down through generations lost forever.

“Under my leadership the Conservative Party will staunchly oppose the family farm tax, which threatens our vital rural economy and our food security, with increased costs and a greater reliance on imports.”

Victoria Atkins MP, shadow environment secretary, said: “Labour’s cruel family farm tax will destroy the farming industry as we know it. Farming families who have farmed their land for generations will be forced to sell it off to pay Labour’s tax bill.”

Reform’s Rupert Lowe said the Government’s attack on the sector will “change British farming forever”.

He said: “Labour’s farming tax will force thousands of farming families to sell the farm to pay the inheritance tax bill. Farms that have been in those families for generations – if it were not for this tax, they would never dream of selling.

“It’s really that simple, and it will change British farming forever. “This is a tax drawn up by people who have no understanding of agriculture. There are three farming MPs in Parliament, I am one of them.”

Mr Reed said: “Farmers are the backbone of Britain, and we recognise the strength of feeling expressed by farming and rural communities in recent weeks. We are steadfast in our commitment to Britain’s farming industry because food security is national security.

“It’s why we are investing £5 billion into farming over the next two years – the largest amount ever directed towards sustainable food production, rural economic growth and nature’s recovery in our country’s history.

“But with public services crumbling and a £22 billion fiscal hole that this Government inherited, we have taken difficult decisions.

“The reforms to Agricultural Property Relief ensure that wealthier estates and the most valuable farms pay their fair share to invest in our schools and health services that farmers and families in rural communities rely on.”

Meanwhile Downing Street has refused to be drawn into a row with Elon Musk after the tech billionaire described the Government as “going full Stalin” in its approach to farmers.

Mr Musk made the claim on X, formerly Twitter, the social media platform he owns.

The businessman, who will advise Donald Trump’s incoming US administration, shared a screenshot of a newspaper article titled “Farmers have hoarded land for too long. Inheritance tax will bring new life to rural Britain”.

The opinion piece predicted that changes to inheritance tax relief for farmers made by Ms Reeves at the Budget could lead to a break-up of the largest farms, giving younger farmers a chance to buy land and enter the industry.

But Mr Musk was more critical of the reforms in his response, writing in a repost: “Britain is going full Stalin.”

The billionaire’s claim appears to be a reference to Soviet leader Joseph Stalin’s forced collectivisation of once privately owned farms, which brought them into state control between 1928 and 1940.

Asked for a response to Mr Musk’s criticisms, Downing Street said it would not “get into a back and forth on individual comments”.

A Met Police spokesman said the force was “well prepared” for Tuesday’s protest and had had positive discussions with its organisers.