Plans by the Prince of Wales to sell off up to 20% of the Duchy of Cornwall could see more tenant farmers across England asked to buy their farms or move out.

Up to 40 farm holdings across Devon, Cornwall, Herefordshire and the Midlands could be affected by the sale, according to the Tenant Farmers Association (TFA).

Locals say talks over the future of nine farms on the Bradninch estate in Devon have already caused “distress” for some tenants who fear they cannot afford to buy.

A spokeswoman said the Duchy could not confirm the total number of tenants affected by the ten-year sale plan , externalbut told the BBC the estate was “supporting them through the process with care and respect”.

The Duchy, which covers around 51,800 hectares (128,000 acres) in 19 counties, plans to use the £500m raised from the property and land sale over the next decade to invest in local communities, affordable housing and environmental projects.

Former GP Mary Ryan, a local Lib Dem councillor who has lived near the Bradninch estate for around 35 years and is supporting the farmers, said some of those affected were “experiencing enormous mental and emotional distress” as a result of the planned sell-off.

She added that while the Duchy had reportedly apologised to tenants last month, the handling of the process had been “pretty dire”.

The sales programme has now been extended from Bradninch, near Cullompton, to the Duloe Estate in Cornwall and to individual holdings elsewhere in Cornwall, Herefordshire and the Midlands, according to the TFA.

The Duchy’s rural director, Matthew Morris, told the BBC he was listening to feedback over how the sales were being handled and offering support and mental health advice to tenants.

Morris added that the Duchy was “still committed to agriculture” but that there “may well be other disposals in the future”.

In terms of immediate evictions, he said, there were “no cliff edges here” and that the Duchy was working closely with every tenant to find a suitable outcome.

“In the main, our mission is to sell to our farmers. We are keen that wherever possible we can achieve that continuity,” Morris explained.

“For many of our farmers, it’s a generational aspiration to own their farm. A few people have said it to me: ‘My grandfather wanted to buy his farm. My father wanted to buy the farm. And now I’ve got the opportunity and it’s an amazing outcome’.

“That’s kind of what’s driving me through what, at times, has been a little bit of turbulence.”

The Duchy – which was established in 1337 – currently has around 700 agricultural lettings, with around 300 whole farm holdings made up of a farmhouse, land and buildings.

Farmers are on a mix of contracts ranging from time-limited to lifelong, with an option to pass the tenancy down through a family.

George Dunn, TFA chief executive, said the organisation was in “deep discussions” with the Duchy and that poor communication had led to tenants “facing prolonged uncertainty over valuations, timing and the options available to them”.

“Once a family is told that its long-term relationship with the Duchy may change permanently, that uncertainty lives with them 24/7,” he told the BBC.

He added that while he welcomed the Duchy’s assurance that “nobody will be made homeless” not every tenant “will be able or want to buy the farms that they operate and fair alternatives must be explored for those for whom ownership is unaffordable”.

A spokeswoman for the Duchy said: “We are engaging with people directly and supporting them through the process with care and respect.

“We recognise that each of our tenant’s circumstances are different, and we are taking a careful, case-by-case approach.”