Farmers forced the prime minister to cut short a visit to a housing development as they drove tractors to the site in a protest against changes to inheritance tax.
Sir Keir Starmer was in Buckinghamshire to announce more than 100 new towns could be built under the government's plans for the "largest house building programme since the post-war era".
Politics latest: Follow live reaction to PM cutting short visit
As he spoke to workers at a housing development in Milton Keynes, a group of farmers gathered in about a dozen tractors outside the site.
They sounded musical horns, disrupting the announcement shortly after Sir Keir arrived.
The prime minister cut the visit short following the protest, driving off before he was set to do media interviews.
Farmers have staged several protests since the October budget, when the government introduced a 20% inheritance tax on farms worth more than £1m from April 2026.
They have accused the government of failing to listen to them and said the tax will mean some will have to sell off land or their entire farms to pay for it, which could affect food production.
Sir Keir later said his government had made a "political choice" to grow the economy and bring NHS waiting lists down instead of maintaining "the tax break for farmers".
"People watching this will understand that that is a choice. They will know what they would prefer," he said.
"Do they want their waiting lists to come down, do they want their mortgages to come down, the economy to start working for everyone?
"That is what we are trying to achieve.
"Or do we want to give tax breaks for farmers? We can't have both."
Farmer Phillip Weston told Sky News' Dan Whitehead at the protest: "He's not coming to us to talk, so we're coming to him."
As Sir Keir was driven away from the site, farmers could be heard shouting "just talk to us".
Farmer Richard Miles, who travelled from Welford, Northamptonshire, said: "We are not being listened to at all, that's why we feel we have to come and see him in person."
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A Thames Valley Police spokesman said: "Thames Valley Police facilitated a peaceful protest off the A509 and liaised with the protesters at the scene.
"Officers from the local policing team engaged with the protesters.
"No arrests were made or necessary. The protest has reached its conclusion and the group are now dispersing from the area."
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