America's former chief transport inspector is calling on Boeing to make major safety improvements at its plants.

Boeing workers have come forward with fresh safety concerns about the company's factories.

The plane-maker has dismissed claims shoddy production and weak oversight are compromising the safety of its jets.

But Mary Schiavo, a former inspector general of the US Department of Transport, told Mike Yardley the claims are serious and need to be addressed.

She says aircraft factories need almost surgical cleanliness, to ensure they are producing safe planes.

Boeing has been under intense scrutiny since two of its 737 MAX planes were involved in deadly crashes just months apart, killing over 300 people.

This resulted in countries around the world grounding the best-selling commercial aircraft out of fear another crash would occur.