The Home Office reckons there are currently between 310,000 and 570,000 undocumented workers in the UK but these figures are widely believed to be a huge underestimate.

It took the News of the World undercover reporters less than two days to entrap 66 undocumented in London. All they had to do was to pose as gang masters seeking cheap labourers.

The first buslaod came from the East End, where the newspaper using it's undercover reporters put out the word that they needed day labourers.

Yesterday at 9.30 am, a 53-seater coach pulled up outside the Ruskin Arms pub in East Ham. Scores of workers, some clutching lunchboxes, piled on board.

The second bus came from outside a Sikh temple in Southall into which squeezed 21 workers

To the surprise of all the workers, BOTH buses headed straight to the Colnbrook Immigration Detention Centre near Heathrow where 25 uniformed police officers stood in wait.

The convoy was ordered into a secure compound where 35 immigration officers swooped.

Each man was searched and placed in detention. All mobiles were confiscated.

Last night a Home Office spokesman confirmed that of the 70 workers the News of the World delivered, 66 people had been arrested and detained. Among them were EIGHT failed asylum seekers already sought by immigration.

The Home Office said: "We are grateful to the News of the World for its work to bring these cases to light. Tackling illegal working is a top priority."