Rogue landlords in England who commit housing offences should be fined a minimum of £30,000 by magistrates to help drive up standards in the private rental sector, the Local Government Association (LGA) said.
It said English Housing Survey figures show 27% of privately rented homes failed to meet decent homes standards in 2016 and 8% of properties had damp problems.
Councils can enforce fines of up to £30,000 on private landlords for offences such as not complying with an improvement notice.
But the LGA said there should be more consistency across the courts, with common sentencing guidelines.
Councillor Martin Tett, LGA housing spokesman, said: "A key deterrent to rogue landlords would be for the Government to set common sentencing guidelines which delivers consistency across the courts.
"It is not right that the level of civil penalty could outweigh that which is handed out by magistrates."
He continued: "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."
Mr Tett said the majority of landlords are "decent, responsible law-abiding citizens who do a great job in making sure their tenants are living in safe and quality housing".
He continued: "Unfortunately there is a minority of rogue landlords who give those good landlords a bad name."
Richard Lambert, chief executive of the National Landlords Association (NLA), said: "The NLA supports making the punishment fit the crime because too many of the criminals who operate in the private rented sector see the current level of fines as little more than a cost of doing business, and we would welcome greater consistency between civil and criminal penalties.
"However, establishing a £30,000 minimum fine goes too far in the opposite direction. Disproportionate punishments end up discrediting the whole system."
Mr Lambert said local licensing schemes can be very effective when they are well targeted and backed by properly co-ordinated and funded enforcement.
But he said too many have been introduced "without any thought having been given to how to deal with what will be thrown up as a result".
A Ministry of Housing, Communities and Local Government spokesman said: "Everyone deserves a safe and decent home and we have given councils strong powers to crackdown on bad landlords and we expect them to use them.
"Since April 2017, local authorities have been able to issue civil penalties of up to £30,000 as an alternative to prosecution to cover illegal eviction or failure to comply with a statutory notice.
"We believe that a fine of up to £30,000 acts as a significant deterrent to rogue practices."