AN OVERWORKED Hampshire air traffic controller sent two passenger planes on a collision course.

As a result of the error the two passenger jets came within 700 feet (213 metres) of each other, according to a near miss report.

The error was made by a controller at the £700m Swanwick-based air traffic control centre ''during a period of high workload'', the UK Airprox Board (UKAB) said.

He gave an instruction to increase altitude to a Boeing 737 leaving Stansted Airport, Essex, which was meant for another aircraft from the same airline, the UKAB said.

This caused the former to climb ''into confliction'' with a Boeing 777 approaching the airport, according to the report.

The official minimum separation between the two jets should have been 1,000 feet (305 metres).

After realising his mistake the controller gave further instructions, but the pilot of the Boeing 737 claimed these were ''very unclear'' and he ''sensed some confusion from the controller''.

The pilot described the risk of collision as ''medium-high''.

The incident occurred at 6.57pm on April 1.

Some members of the UKAB suggested the controller may have been ''overloaded''.

The report concluded: ''The board quickly agreed that the airprox (near miss) had occurred because the controller had inadvertently instructed the wrong aircraft, B737, to climb into confliction with the B777.

''In mitigation, it was apparent to the board that, at the time of the airprox, the controller's workload was high.''

A spokesman for NATS said: “On 1 April an air traffic controller at the Swanwick Control Centre mistakenly allowed a B737 leaving Stansted to fly at less than the required level of separation – 1,000ft or 3 miles - with a B777 aircraft.

"The controller took action to correct the error and the UK Airprox Board concluded that there was no risk of collision.

“Incidents like this are rare and NATS has an excellent safety record, but when they do occur we always seek to learn the lessons to help avoid any potential repeat.”