Private landlords have branded a new licensing policy as "a sledgehammer to crack a nut".
A registration scheme proposed by Newcastle City Council would require them to pay up to £750 per property.
More than a hundred have held a meeting to discuss opposition to the scheme, saying it would penalise good landlords and raise rents.
The council said it would improve accommodation and local neighbourhoods and reduce anti-social behaviour.
Landlord Bruce Haagensen said the council's evidence showed only a small number of landlords were "not doing things correctly".
The scheme would affect about 19,000 properties.
"Even if you say 10% are bad that still leaves 17,000 who are good and are being forced to pay money for a licence that really isn't relevant to them and is ultimately going to push rents up for tenants," Mr Haagensen said.
More than 24,000 homes in the city are privately let and landlords can already be fined for ignoring certain responsibilities.
The council said it receives about 1,200 complaints a year concerning private accommodation.
Housing team leader Paula Davis said there were an "awful lot of very vulnerable tenants" in the city.
"Old people, young people, people who have migrated into the city and maybe don't speak English as a first language - and they just wouldn't know who to complain to," she said.
The scheme would require landlords to meet a number of conditions and pay a fee to obtain a licence which would last for five years, or one year for landlords with a history of poor compliance, showing their property met certain standards.
Ms David said some landlords thought renting was "nice easy money".
But it was "absolutely vital" they understood that "if they fail to comply, there will be consequences", she said.