A computer error that saw around 900 business class airfares sold at economy prices has driven a wedge between Australian travel agents and Singapore Airlines.

It is understood the fares for flights between Singapore and European destinations were incorrectly loaded into the system by the airline.

As a result about 900 of the “cheap” fares were sold by online agents in Australia between Saturday and Monday.

But now Singapore Airlines is demanding agents inform their clients of the issue and charge them the difference — which in some cases is as much as $5000.

Travel agents who do not recover the money from clients have been told they will have to pay up themselves.

A Singapore Airlines spokeswoman confirmed the airline had “recently reassigned a booking subclass originally designated to economy class bookings to be used for business class bookings from December 8, 2014”.

“We have been notified that a small number of travel agents have sold tickets against this reassigned business class subclass, at an economy class fare level,” said the spokeswoman.

“The airfare conditions for the fare clearly stated that it was only valid for economy class travel.”

Travel agents who do not recover the money from clients have been told they will have to pay up themselves.

A Singapore Airlines spokeswoman confirmed the airline had “recently reassigned a booking subclass originally designated to economy class bookings to be used for business class bookings from December 8, 2014”.

“We have been notified that a small number of travel agents have sold tickets against this reassigned business class subclass, at an economy class fare level,” said the spokeswoman.

“The airfare conditions for the fare clearly stated that it was only valid for economy class travel.”

A Flight Centre spokesman said they became aware of the issue on Saturday and notified Singapore Airlines - but the problem was not rectified until Monday.

“The fare showed up in the booking system that online and bricks and mortar travel agents use as a business class fare, although it was also listed as economy in the fare rules - hence our messages to the airline over the weekend,” he said.

“We have a good relationship with Singapore Airlines and will continue to talk to its management team in Australia to hopefully ensure a good outcome for our customers who have been affected.”