A BBC investigation has revealed serious security lapses at Manchester Airport after an undercover reporter spent 10 weeks working there.

While Michelle Cox was working as an aviation security officer, she claims she was encouraged to flout Department for Transport rules on bag searches.

The BBC also claims she found planes left open and unattended overnight and that staff knowingly used faulty metal detectors.

The airport said travellers' safety was its "highest priority" and any breaches in procedure were fixed "immediately".

The BBC show is being screened on Tuesday at 9pm on BBC1 as part of the Whistleblower series.

A spokesman said: "Manchester Airport's procedures, systems and equipment are part of a robust effective defence system comprising several different levels, which changes and evolves as necessary.

"Together with regular reviews and inspections, this provides an intricate system of checks and cross-checks which taken together provide a robust security net. We take any allegations of shortcomings extremely seriously and any breaches in procedure are rectified immediately."

Programme makers said on one occasion around 1,000 passengers passed through the airport from Pakistan but only three random bag searches took place.

They added: "Michelle was told by colleagues to exaggerate the figures, with one workmate openly declaring 'We cheat'."

The reporter was also able to gain access to one of the planes and film undisturbed, the programme said. The BBC also claims the film will show a metal detector failing to sound when a knife and gun were passed through it as part of a test.

It said: "The detector failed to go off on a number of occasions and was shut down.

"The second detector in the area was tested with a large pair of scissors and also failed to go off on a number of occasions.

"This one was not shut down and staff continued to allow approaching passengers through security using the unreliable machine."

Security team leaders are also alleged to have tipped off colleagues about covert DfT inspectors, phoning their physical descriptions through to colleagues.