Farmers across numerous sectors have seen incomes plummet, new Defra figures show, with the NFU calling the outlook for many 'stark'.
Defra has published its Farm Business Income figures, which estimate that for cereal farmers, incomes have fallen by a significant 73%.
And for dairy producers, incomes have plummeted by 68 percent compared to 2022-2023.
Farmers across the country have had to deal with rising input costs and significantly lower commodity prices over the past year.
On top of this, businesses have seen a reduction in direct payments and one of the wettest winters in decades.
The grazing livestock sector - lowland and least favoured area (LFA) - have seen a 24% and 12% fall in income respectively.
The mixed sector saw a 67% fall in income, while for growers in the horticulture sector, incomes plummeted by 38%.
NFU President Tom Bradshaw said Defra’s estimated figures for 2023-2024 showed a 'stark picture' of the challenges facing many farmers.
He said that the recent budget changes to agriculture property relief (APR) and business property relief (BPR) has also left farmers 'reeling'.
"Many will be faced with a tax bill of millions - some will be forced to sell all or part of their farm to raise the funds," he warned.
The Treasury has said 73% of APR claims are below £1 million and so would be unaffected by this policy.
However, Defra’s own figures show that just over a third of farms are under £1 million net worth.
The NFU said the Treasury’s figures were based on past APR claims and did not consider farms that had also claimed BPR for diversified aspects of their businesses.
They also included a substantial number of smallholdings, with 27% of those Treasury figures being for assets under £250,000, and another 23% under £500,000.
The union said that very few viable farms were worth under £1 million, as that could 'buy 50 acres and a house today'.
Mr Bradshaw said: “Another key question is what impact assessment has been done ahead of this policy announcement on homegrown food production?
"Because if farms are being broken up and sold, British food will be hit. There is a very real threat to our long-term food security because there is no incentive to invest for the future.
"Any available cash will now be going into pension provisions rather than investing in the infrastructure on farm to deliver food security for the next decade and beyond."
He added: “The only sensible course of action is for the Treasury to reverse this decision and soon.”
The NFU has organised a 'mass lobby of MPs' event, taking place on Tuesday 19 November, which will be attended by 1,800 farmers and is at full capacity.
The venue for this is the Church House conference centre in Westminster, where farmers will ask their MPs to 'look them in the eye' and tell them whether they support changes outlined in last week's budget.
At the same time, and independent of the NFU's rally, thousands of farmers are expected to protest on the streets of Westminster, with those wanting to attend urged to register now.
