Local authorities are failing in their duty to prosecute criminal letting agents, the National Landlords Association (NLA) has warned.
The NLA says a lack of enforcement is undermining efforts to improve the reputation of the private rental sector.
More than half of 20 local authorities did not prosecute a single letting agent between 2014 and 2018, according to a Freedom of Information (FoI) request made by the organisation.
The FoI request reveals that 32% of the 20 authorities contacted prosecuted three agents or fewer.
Of the 20 councils questioned, 13 had already introduced landlord licensing schemes and the NLA has identified Hammersmith and Fulham as not bothering to respond to the FoI request.
It pinpoints Liverpool City Council as the outlier in its sample of local authorities, following the council's 13 convictions of agents between 2014 and 2018.
The NLA says letting agents play an important role as intermediaries between landlords and tenants, but accuses some agents of making 'unauthorised alterations' to landlords' properties.
It says some agents also let landlords' properties to multiple renters, creating illegal Houses in Multiple Occupation which can leave the landlord liable to significant fines or criminal charges.
"Too many local authorities [are] failing in their duty to prosecute rogue letting agents. These bad ones can really poison the relationship between landlords and tenants," says Richard Lambert, chief executive of the NLA.
"We want to see local authorities take much firmer action."
"While many local authorities have introduced licensing schemes to crack down on rogue landlords, they seem to be allowing letting agents to get off scot-free," he says.