Passengers trying to get through Stansted airport are being hit by long delays because the sun’s rays are confusing the sophisticated cameras used at border control.

The passport hall at the airport faces west, meaning that during summer evenings the cameras point straight into the setting sun. Last week border guards at the airport, which is used by more than 23 million passengers a year, were overheard discussing a “high rate of rejection because of the sunlight”.

Passengers arriving at Stansted are funnelled into a passport hall and divided into two queues, one for those with biometric passports and the other for those with older or non-European Union passports.

Biometric passports contain a chip carrying data for facial recognition cameras. This is meant to speed the process of people passing border controls. However, at Stansted the cameras are repeatedly failing to read the face of the passenger, who then has to go to the back of another queue.

Ralph Gross, of the Robotics Institute at Carnegie Mellon University in Pittsburgh, Pennsylvania, said the sun setting behind passengers would pose a challenge for the system’s face recognition algorithm.

“It’s got better at dealing with challenging illumination situations, but it will still struggle in this light. As long as the cameras are set up this way, they are going to struggle with the accuracy rate in this situation,” he said.

Gross added that the technology for facial recognition cameras was improving but would not yet work in these circumstances. “It’s the same way as any camera will struggle when it is pointed into very bright sunlight. The human eye is very well-adapted to handle bright lights, and the cameras are getting better but they are still not perfect.”

A Home Office spokesperson said: “Border Force is working with Stansted airport to resolve this issue, which has no impact on border security or the experience for the vast majority of passengers passing through passport control.”

A spokesman for Stansted said the airport was aware of the problem and had recently installed 15 more e-gates to let passengers travel through border control, bringing the total number to 30. All the e-gates currently face the setting sun.