Research from Simple Landlords Insurance describes local authorities as having "no idea" how many unlicensed HMos are operating within their areas after new regulation came into effect earlier this year.
The new rules demand that those who rent a single property to five or more people from at least two separate households who share basic facilities, such as bathroom or kitchen, must ensure that they possess an HMO license - regardless of how many storeys the property comprises.
However, reports show that 85 percent of the 90 LAs it received freedom of information requests from don't know how many unlicensed HMOs are operating in their area.
Furthermore, the research shows that 34 percent have "no idea" how many properties now require a license, and that over the last 12 months, 103 HMO licenses were rejected versus 18, 881 granted.
The report also reveals the extent of how much the new regulations are changing the landscape.
In Greenwich, the area with the largest expected increase, before 1 October there were 147 properties that required an HMO license. That number has since jumped to an estimated 3,250 - growth of 2111 percent.
Richard Truman of Simple Landlords Insurance comments: "The HMO licensing changes may be well-meaning, but a failure to support Local Authorities to communicate about them and enforce them us bad news - for good landlords and for tenants.
"Traditionally, landlords can be resistant to regulation as it can make daily landlord life more difficult. But many are increasingly seeing the lack of structure and national standard as part of the problem.
"We want to see the emerging class of professional landlords supported by central government and local authorities - and that might well mean we need to see more effective regulation and resource."
In early November, the government announced a £2M funding boost for councils to tackle rogue landlords, with housing minister Heather Wheeler saying " This funding will help further strengthen council's powers to tackle rogue landlords and ensure that poor-quality homes in their area are improved, making the housing market fairer for everyone."