Holiday Extras has been forced to defend itself against complaints from agents that it has been direct selling to their customers.
Agents took to the travel industry Facebook group Travel Gossip after receiving follow-up emails to bookings with special online offers.
One said she had booked several customers using her own email, to prevent the customer from receiving spam.
But she had then received emails directly from Holiday Extras offering up to 15% off for airport parking.
She questioned whether Holiday Extras would have paid her commission had one of her customers taken advantage of the offer and made a booking.
Other agents said they had been annoyed to receive the same email, particularly from a company which claims to be trade friendly.
Holiday Extras insisted there had been a mistake and it was investigating.
A spokesman said the company has a great relationship with agents and added: "It is of the utmost importance to us that agents understand that we respect their businesses.
"Our aim is to help and support them to make the most of selling add-ons – and to earn good commission levels from these sales. If, after a full investigation, it is discovered that we had sent an email in error, as a result of an initial booking that was made with an agent; then we would reimburse the agent’s commission.
"We invite any agent with concerns regarding email sends to please contact their partnership development manager or email us at [email protected]."
