Almost two thirds of mortgage advisers said their clients have experienced conditional selling in the past three months.
Of this group, all said the practice had caused their clients stress, hassle or confusion.
Access Financial Services surveyed their advisers and CEO Karl Wilkinson slammed the "broken" property industry.
In the six months to May, 63 per cent said their clients had experienced conditional selling, the practice of a prospective homebuyer being told they must use an agent's in-house services like a broker or solicitor.
Wilkinson said: "Something is broken in the property industry when this practice continues after 20 months of our campaigning against conditional selling, and developing tools and processes to protect advisers and their clients.
“A significant minority of estate agents are being allowed to continue to negatively impact our industry. This has to stop.”
A third of advisers surveyed believed that conditional selling had become worse in the six month period, while the same proportion thought the problem was about the same.
Examples given by advisers about the problem included customers who were denied the opportunity to purchase a property because they refused to choose the agent’s broker.
Wilkinson added: "Conditional selling is morally wrong and a clear breach of consumer duty as well as The Property Ombudsman’s Code of Practice and the Estate Agents Act 1979.
"What other industry puts up with this kind of harmful behaviour? We can do better.”
In November 2022, Access Financial Services launched a campaign against conditional selling which included free letter templates for advisers and their clients.
One was to estate agents making them aware of the situation and, failing a positive response, a second letter to request support from the Property Ombudsman.
tara.o'connor@ft.com
What's your view?
Have your say in the comments section below or email us: ftadviser.newsdesk@ft.com
