Almost 200 owners of shared houses were sent formal notices for breaching planning rules in Brighton and Hove over the past year.
Dozens more shared houses were the subject of complaints in the same period – the year to the end of March.
The figures were revealed on Wednesday (September 4) to members of Brighton and Hove City Council’s Planning Committee.
Principal planning officer Robin Hodgetts said that a large proportion of his work was taken up with concerns about shared houses – also known as houses in multiple occupation (HMOs).
Mr Hodgetts said that his team had reviewed 400 licenced larger HMOs to check their planning status in 2018-19.
He told the Planning Committee meeting at Hove Town Hall that 190 of them had “unknown” planning status and their owners or agents were sent a planning contravention notice.
So far 126 owners had responded – as they are legally required to do.
Mr Hodgetts said that, separately, 66 new HMO cases had been reported in the past year.
This was down from 95 in the previous year and 192 in 2016-17.
He said that, of 38 formal enforcement notices served, 17 related to unauthorised HMOs.
Mr Hodgetts said: “The drop in numbers is good news. There are not many that open without us being informed.
“People living in these areas will let us know. We hope the number of unauthorised HMOs is dropping.”
From April 2018 to March 2019, 587 new enforcement cases were opened and 598 were closed, with some carried over from the previous year.
Officials found no breach of planning rules in 318 of the 598 cases and they negotiated a resolution – or planning permission was granted – in a further 126 cases.
They ensured compliance in 26 cases and 128 were not pursued because there was deemed to be a lack of harm.
One example involved boundary fences which could be two metres high without needing planning permission.
Mr Hodgetts said that if someone built a fence just over two metres high and it did not cause harm, such as overshadowing, the case would probably not be pursued.
He said that his team would be more likely to take action against a big company than a home owner who was badly advised by their builder.
Green councillor Leo Littman said: “Councillors are often contacted about breaches that have taken place but no action has been taken.
“It is frustrating for them when people who make a complaint are given this sort of feedback.”
People were given basic information about why breaches were not pursued.
Conservative councillor Joe Miller questioned the decisions made about whether it was worth following through on a breach.
He said: “I have had cases where residents feel structures have affected them.
“It makes people wonder what’s the point of the planning system. Where do we draw the line?”
Mr Hodgetts said that the key element was harm.
Labour councillor Daniel Yates asked about the number of unallocated cases – down from 400 to 200 – but which still needed to be addressed.
The Planning Committee was told that 38 formal enforcement notices were served in the past year.
So far nine had been complied with. Five were the subject of an appeal and one had been withdrawn. The others are awaiting determination.
A total of 24 appeal decisions had been received during the year, with 10 dismissed, 10 were allowed and four where the decision was split.
Mr Hodgetts said that the Planning Department was reviewing why it had lost 10 appeals – a higher proportion than other councils.
Labour councillor Tracey Hill, who chairs the Planning Committee, said: “These statistics show how busy the service is and how it is helping to protect against unauthorised development, harmful alterations to historic buildings and neglect of properties and land.
“A high number of reports were shown not to have planning breaches and we will be carrying out further research with a view to reducing these so that our team can concentrate on cases where a breach has occurred.”