A Huddersfield woman claims house-builders have put up a metal fence through the middle of her garden.
Gillian Arnold likened the action to "bully-boy tactics" after workmen put up the fence on Wednesday morning.
Lawyers for Leeds-based Camstead Homes said the land, off Abbey Road in Shepley, forms part of the Shepley New Mills development.
But Ms Arnold, who claims to have maintained the land for almost 20 years, disagrees.
She said: "We have been in dispute [about the land] since last year. They say it's theirs. But it's not in their plans and they don't show it being used. They warned me they were going to [put the fence up]. I said they couldn't because we were in dispute [about the ownership] but they have decided that the land is theirs."
Ms Arnold claims to have not received a recent letter in which Camstead Homes said it detailed its intent.
She believes the developers were "out of order", as reported by the Local Democracy Reporting Service.
"My take would be that because the land is disputed, they should not be on there, concreting enormous posts into my garden," she said. This is bully-boy tactics."
A Camstead Homes spokesman said: "The company has legal ownership of the land in question. It has erected a fence around its property to secure it, pending development. It would not be appropriate for us to comment any further in relation to this private matter."
Conservative councillor John Taylor, who represents Kirkburton ward, said he was "gobsmacked" when he saw the fence.
He said: "This is clearly a legal boundary dispute that needs settling through the courts."
Ms Arnold said she was considering legal action.
Kirklees Council approved plans to build up to 34 homes on the site in May 2020.
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