A new undercover operation by Which? is said to show that some estate agents are misleading home buyers about their in-house mortgage broking services.

A total of 29 branches were visited in April by researchers posing as first-time buyers. The branches were in Birmingham, Colchester, Maidenhead and Maidstone. The names of the agents have not been revealed.

Of the 22 that offered in-house mortgage services, not one said that the buyer had to use them.

However, according Which?, six (27%) said that using their own in-house mortgage broker would make a beneficial difference to the property purchase.

Three said that their in-house broker would get the buyer better deals than they’d find elsewhere, and one said it would make the home buying process quicker, and one said that the seller might accept a lower offer.

Reasons given for an in-house broker making a difference to their purchase included:

The sale won’t fall through so you’re in a ‘better position’; it will be quicker to get a mortgage or to complete the purchase; the agent can keep an eye on progress and keep clients updated; clients are more likely to accept an offer from buyers getting their mortgage in-house; the process is smoother; sellers may be more willing to accept a lower offer.

Which? also said that its undercover researchers asked if the agent would receive a referral fee if they used the recommended broker.

Half of the agents said they would, six said they would not, and seven were unclear.

The new research follows a survey by Which? in December which found that 17% of potential buyers said their agent would not be allowed to go on viewings unless they used the in-house broker.

Which? has its own mortgage advisers.