Nicholas McGeehan, director at the UK-based human rights organisation FairSquare, said the working hours of the labourers at The Line were "way beyond what the international minimum standards permit".

"The reality is that workers all over Saudi Arabia are subject to deeply abusive and dangerous exploitation. The abuses are systematically happening across the country," McGeehan said.

Migrant workers make up three quarters of Saudi Arabia's workforce and are critical for the Vision 2030 projects.

Based on data released in India, Bangladesh and Nepal, the film reports that 21,000 foreign workers from the three countries have died since Vision 2030 was launched eight years ago in 2016.