Private landlords should play a much larger role in stabilising the housing market, campaigners have urged.
Ministers are being urged to set standards for renting
The call comes as charity Shelter Scotland is holding a conference in Edinburgh on the private rental sector.
Shelter wants basic minimum standards in addition to new measures for registering private landlords as part of anti-social behaviour legislation.
Director Liz Nicholson said high quality rented accommodation was good for the housing market as a whole.
Ms Nicholson applauded the revival of private renting in recent years but said the reputation of good landlords was being put at risk by a minority of cowboy operators.
The register of landlords forms part of the Anti-social Behaviour (Scotland) Act which was passed in June.
Shelter wants the scheme to go further, towards "a light-touch certification" system to sets basic standard and weed out the worst landlords.
Ms Nicholson said: "The private rented sector in Scotland has grown in recent years but it is still one of the weakest in Europe.
"Too many tenants are put off renting because of the very varied quality of service they get.
"That is why I want to see the worst landlords brought to account.
"This will not only help tenants, it will be good for responsible landlords as well."
She added that high quality, competitive rentals could offer an alternative to home ownership and put a brake on house prices.
The proposals are being submitted to the Scottish Executive as part of the private sector housing bill announced by First Minister Jack McConnell earlier this week.
The Shelter Scotland conference is taking place in Edinburgh on Friday.