A 100-strong unit of "non compliance" officers authorised to conduct interviews under caution is standing by to visit homes where the census is not filled in, it has emerged.
The enforcers have been given powers to gather evidence against householders who decline to complete Sunday's national survey, said a spokesman for the Office for National Statistics (ONS).
Anyone who repeatedly refuses to take part will face criminal prosecution and a fine of up to £1,000.
More than one million people were missed during the last census in 2001, but only 38 were prosecuted, and the ONS is trying to step up targeting of householders who do not comply with the obligation to fill in the form.
From April 6, a force of 30,000 "collectors" will begin visiting households that have not yet completed the census to try to catch people at home.
Glen Watson, the census director, told the Daily Telegraph that the 100 "non-compliance" staff had been recruited to gather evidence for potential prosecution in the case of those who repeatedly refused to take part.
He said: "It's a last resort but we expect to have to take action against some who are persistently refusing. Ultimately, it is a fine and a criminal record."