Some 27 London boroughs said they had no problem with properties being let for short periods and this did not require any planning permission.
But Southwark, Tower Hamlets, Islington, Kensington and Chelsea, Westminster and Camden warned people who let properties for short periods without planning permission could be served with enforcement notices.
In some cases they could receive fines of up to £20,000 if they were deemed to be repeat offenders.
Chief executive of the National Association of Estate Agents, Peter Bolton King, said: "The problem here is a lack of a level playing field which means regulations are not being policed in the same way across London.
"I think it's time for a review and to look at whether this is working or not."
