There is a "widespread" problem of sub-standard conditions in rental properties across Oxford city, a councillor claims.
Some sub-standard homes are escaping inspection
With more than 1,000 complaints last year Councillor Patrick Murray wants more residences licensed.
Currently only those with three floors and more than five tenants require a licence.
The council said a quarter of all houses in Oxford are privately rented but only 15% are currently licensed.
Some landlords were evading licensing by either evicting tenants or leaving a floor unoccupied, Mr Murray said.
His proposal, which is being discussed by Oxford City Council, is to eventually license all properties with two floors and more than three tenants.
But Elizabeth Brogan, of the National Landlords Association, said some landlords do not want to share the "administrative burden" of licensing.
"Many landlords could be scared out of letting houses in multiple occupation," she told the BBC.
"They will turn away tenants who are proposing to share houses on joint tenancies even though the houses may have a perfectly good standard and the tenants are perfectly respectable tenants."
However, Mr Murray said: "There are 20,000 students and a lot of young professionals, who can't afford to buy a home, are sharing as a first step.
"The demand is there and it is unlikely that the cost of the licences will put people off."