Landlord campaigners are asking property investors to tip them off about local councils that might be illegally analysing council tax data to identify houses in multiple occupation.
One case is already before the Information Commissioner - the body that polices breaches of the data protection act, says the Residential Landlords Association.
That case involves Portsmouth City Council.
Neither the council nor the Information Commissioner will comment on the case while the details are under investigation.
“The RLA is concerned at the growing number of local authorities using council tax student exemption data for working out the numbers of HMOs in an area when applying planning policies, such as Article 4 directions,” said a RLA spokesman.
“The RLA believes such use may be illegal, and a case involving a council is currently being referred to the Information Commissioner.”
Students are exempt from council tax providing they are registered with an appropriate further education organisation, like a university or college.
if they live in a house in multiple occupation (HMOs), the council can analyse the data to tell how many tenants are at each property and whether the shared house is a small HMO (3-5 tenants or a large HMO (6 or more tenants).
Although all large HMOs are subject to mandatory licensing, around 40 councils also have special licensing schemes for small HMOs.
Councils have also analysed other housing data to identify HMOs - like the payment of housing benefits to tenants who may share rented homes.
Meanwhile, HMO landlords in East Lindsey - around Skegness, Lincolnshire - have had the term of their licences cut from five to three years.
The council explained a string of complaints and convictions against landlords led to the decision in an effort to increase housing standards.
Portfolio holder for housing at the council, Councillor William Gray, said: "Many HMOs in East Lindsey operate to a high standard but sadly some don't. This policy decision means we will have a firmer grip on the standards in licensable HMOs and be better placed to take action should they fail to be maintained to a level that provides a dignified and safe way of living."
