The Duke of Northumberland has been accused of “dereliction by design” as part of proposals to replace allotments with dozens of new homes on his Syon House London estate, a public inquiry has heard.

Ralph Percy, the 12th Duke of Northumberland, lost an application in October 2021 to build 80 flats on part of his Grade I-listed Syon Park estate in west London after the council received more than 900 objections from locals to the plans.

A loss of local open space (LOS) was one reason behind Hounslow Council’s planning committee decision to refuse planning permission.

Strong opposition to the proposals was aired by the chair of the allotment association on Thursday at Hounslow House, in Middlesex.

Northumberland Estates said its plans would help provide an income stream for conservation works to Syon House, which is privately-owned but still open to the public.

Key worker housing for the neighbouring West Middlesex University Hospital has also been promised, and there would still be a place for those who use the allotments, the inquiry heard.

But the chair of the allotment group said the proposal to replace the current allotments with smaller “60 square metre” plots was inadequate as they would only be suitable for “beginners”.

Stephen Hurton, chair of Isleworth’s Park Road Allotment Association since 2016, said people with smaller plots “can’t grow potatoes or brassicas because you don’t have the space”.

Mr Hurton continued: “You can only really do short-term growing. Things like lettuce.

“If you don’t know you’re going to be able to harvest crops then what’s the point of growing them?

“What we’re being offered isn’t sufficient as far as all of the members are concerned.”

Mr Hurton said there had been a “period of uncertainty” for allotment holders under Northumberland Estates, which took responsibility for the site in 2015.

He continued: “We’ve had short-term leases and the threat of closure.

“It’s been dereliction by design with most only being offered short-term lets and a breakdown in communication with the landlord.

“(When they are not re-let) plots become overgrown and it means people feel uncomfortable from a safety point.

“There are lots of people locally who want to be able to grow and don’t have the opportunity.”

Melissa Murphy KC, for Northumberland Estates, said the site had been taken back under management in 2015 because it was “overgrown and underused”.

Local residents, councillors and allotment holders – plus the Labour MP for Brentford and Isleworth and former Hounslow councillor Ruth Cadbury – are among those who have already spoken at the appeal hearing about why they feel the scheme should be rejected.

Claire Nevin, for the Park Road Allotment Association, previously told the inquiry Northumberland Estates was proposing “sacrificing 71% of allotments at the heart of a community they have served for over 100 years”.

It was first used to help the local community in the aftermath of the First World War and “over a century later, the site continues to be a haven for allotment holders, their friends and families as well the wider local community – in good as well as difficult times”.

Ms Murphy previously said “quantitative improvements are proposed” and the project would be a “well-located, well-designed scheme which delivers 40% affordable housing”.

She also noted that Syon House is privately-owned, but open to the public.

Period dramas such as The Madness Of King George, Emma starring Gwyneth Paltrow, and Gosford Park have been filmed there.

The hearing was adjourned to Friday.