An agent has warned agents that some of the free and cheap portals appear to be selling their data feeds to their competitors.

Faisal Yousuf, director at Citydeal Estates in London, said: “I would like to warn everyone out there that some of the low end portals appear to be selling the data feed to other agents, which is used to target properties with marketing mail.”

He told Eye that each time his firm listed one particular property earlier this year, a letter was delivered to that address from another agent pitching its services.

He added: “The problem has just resurfaced. We recently uploaded a property with a slightly incorrect address and the owner of that property called us to say that they are receiving letters from agents offering their services. The owner is angry and fed up.

“We are ensuring our systems only feed subscription portals and any free portals are removed.”

He said other agents may want to do the same.

He added that the only portals Citydeal Estates subscribes to are OnTheMarket and Rightmove.

He admitted that under the “one other portal” rule, his firm should have taken steps to remove itself from other portals, including the free ones.

He said: “The big decision for us was coming off Zoopla. We actually didn’t realise the large number of free portals we were publishing to until recently, and they don’t generate any enquiries.”

He said he is still trying to get to the bottom of what has been going on but has in any case asked to be removed from four websites.