The council’s legal team is considering a solicitor’s letter from the landlords’ association, a spokesperson said.

A consultation is currently running on plans to extend the licensing scheme for houses in multiple occupation (HMOs) in York. Currently all homes containing five or more people from more than one household – for example shared student houses or bedsits – must be licensed to meet certain standards.

Under the proposals, the licensing scheme would be expanded to include all smaller HMOs in areas of the city where there are high levels of shared housing – council wards Hull Road, Guildhall, Fishergate, Clifton, Heworth, Micklegate, Osbaldwick and Derwent and Fulford and Heslington.

The council says the proposals have been put forward because it wants to “ensure our city has a safe, well-managed and professionally run private rented sector“.

But solicitor David Smith, who specialises in residential property rights, has sent a letter to the council on behalf of York Residential Landlords Association.

It says the association’s members are “deeply concerned“. They have three main concerns – they claim that the consultation is unlikely to meet the requirements of a lawful consultation, that the documents accompanying the consultation fail to make a “clearly evidenced case” for the scheme to be rolled out, and that parts of the proposed scheme are unlawful.

It adds: “For these reasons, we consider that any decision to proceed with an additional HMO licensing scheme on the basis of the consultation as it stands is likely to be irrational, unlawful, and ultra vires [beyond the legal authority of] the powers of the council.

“If a decision is made on this basis we will advise our client to challenge it by way of judicial review in the administrative division of the High Court.”

“Our client remains happy to discuss alternatives to a licensing regime and to engage positively with the council.

“However, if the council determines to proceed with a licensing regime on the basis of the consultation then our client will have little choice other than to proceed to issue proceedings for judicial review of that decision.”

Tracey Carter, director of housing at the council, said the local authority has received the letter and it is being considered by the legal team.

She added: “All views expressed through the consultation on our licensing proposal are welcomed and taken seriously.

“This is a statutory consultation which must seek views from all those who could be affected by the proposal including tenants of HMOs and other privately rented homes, landlords, businesses and relevant organisations including the NHS, Citizens’ Advice and the city’s universities.”

View and respond to the consultation at york.gov.uk/HMOConsultation by June 27.