Figures provided by the Residential Landlords Association (RLA) to The Yorkshire Post show just 35 prosecutions were started against private landlords by the region's town halls in 2017/18, down from 48 the previous year.
Over the previous four years only 105 such prosecutions were launched by local authorities in Yorkshire and the Humber, including 26 in 2015/16 and 13 in 2012/13.
And according to data obtained under the Freedom of Information Act by the RLA, across the country two-thirds of councils in England and Wales brought no prosecutions at all against private landlords in the last financial year.
In Yorkshire and the Humber, Bradford and Leeds began the largest number of prosecutions against landlords, with ten each during the whole 12-month period, followed by North East Lincolnshire with four.
The RLA says seven councils, Calderdale, Craven, Doncaster, Hambleton, Kirklees, Selby and Wakefield, took out no prosecutions, while one authority, Harrogate, said it had not recorded the data in 2017/18.
The organisation, which describes itself as the national voice for landlords, says most of the region’s councils are also failing to make use of new powers to issue fines against criminal landlords.
But the body representing local authorities says that legislation "is not keeping pace with the ingenuity of these rogue landlords" and that "councils are determined to do everything in their power to ensure tenants can live in secure properties".
The Government has been urged to improve existing laws to help local councils take action against the rogue landlords who are "taking advantage of those at the sharp end of our housing crisis".
The Local Government Association has called on Ministers to help draft "more cohesive" legislation to tackle those who are making their tenants' lives a misery after claiming that current laws are "not keeping pace with the ingenuity of rogue landlords".
The warning came after figures from the Residential Landlords Association showed that only 35 prosecutions against private landlords were started by Yorkshire councils in 2017/18, with two-thirds of town halls nationwide bringing no such prosecutions during the same period.
David Smith, Policy Director for the RLA, said: “Either the number of problem landlords is not as high as some suggest, or councils across Yorkshire and The Humber have been unable to enforce the extensive range of powers they already have to root out criminal landlords.
"The inconsistent data across the region suggests that it is the latter. This demonstrates that it is not more regulation that is needed but better enforcement of existing law.
“Criminal landlords cause misery for their tenants, undercut the majority of landlords who are decent and bring the sector into disrepute."
Since April 2017, councils have had powers to issue civil penalties of up to £30,000 against landlords found to have breached a range of laws as an alternative to prosecution. But the RLA says that according to data obtained from 21 councils across the region, 17 did not issue any civil penalties.
In response, the LGA, which represents local councils nationwide, said: “Legislation is not keeping pace with the ingenuity of these rogue landlords, and whilst councils are determined to do everything in their power to ensure tenants can live in secure properties, it’s essential that legislation is more cohesive, and prevents the minority of rogue landlords from taking advantage of those at the sharp end of our housing crisis.
“Many councils are already tackling issues in the private rental sector by bringing in landlord licensing schemes, but they are limited in how widely these can be introduced. We need to see these rules relaxed and councils given more freedom and flexibility in establishing schemes."
Two of the Yorkshire authorities who did not bring any prosecutions against private landlords in 2017/18 defended their work.
Tracey Harwood of Doncaster Council said the authority started several prosecutions against private landlords in 2017/18 but they didn't show up in the figures as they didn't conclude until 2018/19.
She said: "In addition, we have continued to use these powers to take legal action against landlords for both routine non-compliance issues and selective licensing breaches.
"We have also recently started to issue civil penalties to landlords who are failing to provide a suitable standard of living for their tenants."
Calderdale Council’s Assistant Director for Economy, Housing and Investment, Karen Lythe, said: “Our focus is on educating landlords and encouraging tenants to come forward if they’re living in sub-standard accommodation. We aim to step up this proactive work in 2019.
“We won’t hesitate to take enforcement action or to prosecute if safety is compromised."
Commenting on the figures, Housing Minister Heather Wheeler said: “Everyone deserves a safe place to call home and we are committed to tackling the minority of rogue landlords who exploit tenants.
“Through fines and banning orders, we have provided councils with new enforcement tools and we expect them to use these powers to crack down on bad landlords. We are also giving local authorities an extra £2m to help them take action.”
According to the 2011 Census, around 16 per cent of households in Yorkshire are in the private rented sector, up from eight per cent a decade earlier.
Yorkshire councils have highlighted their efforts to prosecute private landlords in the last year.
Leeds City Council said a rogue landlord was fined twice in the space of two months and left £14,000 out of pocket for failing to provide a suitable standard of living for tenants at two of his rented properties.
And in Hull, a landlord was fined £2,140 in February, his third conviction in 15 months, for failing to provide adequate management of four flats.