Farmers threaten to blockade Britain's ports and withhold food from supermarkets in response to Rachel Reeves's death tax rise.

Under plans announced in the Budget, inheritance tax (IHT) will be charged at 20% on agricultural assets above £ 1 million. The Chancellor has said that in some cases, the threshold could be about £3m.

While the 20% figure still represents a relief of 50% compared to the standard rate, farming unions and opposition parties have slammed the move, arguing it will make British farms uncompetitive.

The National Farmers' Union is planning a mass lobby of MPs on November 19 to petition parliamentarians to overturn the changes.

But some farmers are now discussing plans for more radical action, including blocking ports and food distribution centres.

One farmer told the Telegraph they will block every port in the UK if they have to, possibly slowing down supermarket supplies.

They added: "The Government and supermarkets need to realise the control we have as farmers."

Clive Bailey, the founder of Farming Forum, told the publication some farmers were mulling, not letting food leave farms or sending livestock to market.

A coordinated "sewage strike" could also see farmers refuse to take sludge from water treatment works to spread on their land, generating huge amounts of waste to pile up.

Mr Bailye said he supported the NFU's lobbying action but added it was "very limited".

Mr Bailye, an arable farmer from Staffordshire, said: "They weren't organising a rally. They weren't organising a march-type event.

"It was becoming very obvious that farmers were desperate for somebody to take the lead and organise something else."

Mr Bailye has organised a separate rally to the NFU event on the same date. He said there were 2,000 registrations in the first two hours of the event's launch.

The farmer said he could see the number of attendees "getting past 10,000", adding: "We're not wanting to take that European, French farmer route of burning tyres in the street and inconveniencing everybody.

"So we're positively saying 'don't bring tractors, don't cause problems, this is peaceful'.

"We want to keep the public on side. We don't want to bring the capital city to a stop or disrupt roads."

NFU president Tom Bradshaw said the union was "supporting" the alternative event. He told the BBC: "What we cannot do is take responsibility for people in the streets."

A Government spokesman said: "The Government's commitment to our farmers remains steadfast. We have committed £5 billion to the farming budget over two years, more money than ever for sustainable food production.

"We understand concerns about changes to agricultural property relief, but the majority of those claiming relief will not be affected by these changes. They will be able to pass the family farm down to their children just as previous generations have always done.

"This is a fair and balanced approach that protects the family farm while also fixing the public services that we all rely on. We remain committed to working with the NFU and listening to farmers."