Many have failed “fit and proper” ownership tests or are among the more than 500 who were hit with housing convictions in England and Wales in 2017.
Here is a selection of the main offenders still renting out properties:
ITV News tracked down McGowan on the street in Hertfordshire, but the landlord who claims to have built a property empire worth more than £30m was not keen to answer questions.
He has had at least six housing convictions since 2014 and been fined repeatedly for the condition of the homes he has let out - while failing a council's "fit and proper" landlord test.
That was Brent Council in north London.
Yet he's still letting out property in Brent - via an agent - and he's still offending, with unlicenced properties and outstanding repairs.
His properties continue to be rented out in Camden, Hertfordshire and Newham.
Tenants at Gary Fixter's homes have faced water flooding down walls, broken fire alarms and dangerous electrics.
Fixter, from Chester, has been convicted across the north of England.
A judge in Wirral in April told him to "give up" the renting game because his properties were so appallingly kept.
Two years ago the landlord was branded "despicable" after being convicted of housing offences in Scarborough, North Yorkshire.
Yet Fixter went on to rent out properties in Chester and Wirral.
Fixter has since sold his properties in Yorkshire and some of those that he owned in Wirral.
Webb has already been deemed “not fit and proper” by Liverpool council and previously been branded "absolutely disgraceful" for a litany of offences.
They include collapsed ceilings, dodgy kitchens and ignored legal orders.
Perhaps most damningly, the former firefighter was convicted for breaching fire regulations in 2016.
He has also been exposed for failing to sort out damp and mould in one of his properties in St Helens, where the repeat offender continues to rent out property.
Goremsandu once earned the unenviable title of “country’s worst landlord” and has continued to be condemned for the state of her properties.
Last year she was banned from managing homes in the London boroughs of Westminster and Haringey for 10 years because of dangerous conditions, including dire fire safety and no fixed heating.
In doing so she became only the second person in Britain to receive a Criminal Behaviour Order for housing, the kind of action usually used to control gang members.
A third party occupies her luxury property in Kensington, west London.
McGuinness is among 28 people listed as "banned" by the London Borough of Newham for failing its "fit and proper" test.
His property empire included a number of dilapidated properties he bought for development and even rented out a converted shed in a bedsit back garden.
But he was convicted for neglecting a number of his properties, with offences including unsafe electrics, damp and even a front door without a lock.
He continues to own property in Ilford, which is licensed by the London Borough of Redbridge, meaning it can be rented out via a third party.
How can landlords still rent after failing a "fit and proper test"?
The current law means it is not illegal for a landlord who has failed the test in one borough to continue to rent out properties in another one.
In fact, landlords can continue to rent out properties in boroughs in which they are banned - as long as the homes are managed by an approved third party.
Even though a landlord has failed a “fit and proper” test, it does not mean all or any of the landlord’s properties are unfit.
How many landlords offended last year and how many were fined?
The survey of criminal landlords carried out by ITV News and the Guardian found:
The number of landlords who together committed a total of 752 housing offences in 2017.
The number of landlords who committed more than one offence in 2017.
The total number of fines in 2017.
The average fine per offence in 2017.
Who received the biggest fines?
The ITV News and Guardian survey of criminal landlords - the most comprehensive yet - found the highest total fine went to Jose Marcos Bispo Rodrigues and his company.
They were hit with fines totalling £190,500 in April 2017 after subletting 15 small rooms to at least 20 migrant workers and students in East London - a former pub property deemed a "death trap" by housing inspectors.
However the singled biggest fine was £150,000, imposed on Bewel Property Ltd in 2017.
That came after six young professionals each paid around £1,000 a month in rent to live in a flat with exposed live wiring and a rotten balcony.
Who had the most offences?
Mustafa Taghdi, an absentee landlord who lives in Libya, had the most convictions for both licensing and non-licensing offences in 2017.
He admitted renting out 16 unlicensed flats and houses in Liverpool.
He had ignored orders from council officers to evacuate a three-storey house with multiple tenants.
The ITV News/Guardian survey was based on FOI responses from more than three quarters of councils in England and Wales with responsibility for the private rented sector.