Chancellor George Osborne told ITV News the government is introducing a new criminal offence for anyone who fails to declare their offshore income.
"The message is very simple. If you are hiding your money offshore, we are coming to get you," the Chancellor said.
ITV News correspondent Lewis Vaughan Jones reports:
At the moment officials must prove that a person holding income offshore intended to avoid paying tax - the proposed changes would mean they would only have to show the money was taxable.
More top news
A team of detectives and specialists is set to begin a painstaking excavation of the area where Ben is thought to have gone missing in 1991.