The AA has admitted that a serious flaw in its recently relaunched website stops some people in newly built properties from getting home insurance quotes.
Customers seeking a quote from the AA have to enter their house number and postcode which are then converted by the site into a full address.
But the postcode database, supplied by the Post Office, is incomplete and fails to recognise many new homes, particularly those built on infill and brownfield sites.
It has led to hundreds of addresses not being recognised.
A spokeswoman for the AA said: “We are dependent on the postcode being accurate and recognised by the system.” She admitted: “It doesn't recognise some, particularly new, postcodes.”
She said this was due to the age of the system, and an updated version was due to go online soon.
Another complaint that has been raised about the site is that when a quote is obtained, the name of the insurer does not accompany the quote, but is tucked away in the terms and conditions of the cover offered.
Association of British Insurer guidelines specify that the name of the insurer should be easily identified.
The spokeswoman admitted: “The AA is aware that it needs to be more prominent.”
She added: “We are currently going through an audit procedure and this is one of the things being examined to see if changes should be made.”
The £6m advertising campaign promoting the site has led to a surge in interest, the spokeswoman said. “We've had a huge upturn in the number of calls we get. It's benefited home insurance especially.”
She said 20% of business was now coming through the web compared with the previous 12% to 15%.