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.
People who avoid paying tax by stashing their money abroad could face a jail term under a new government clampdown.
Chancellor George Osborne is consulting on the creation of a new criminal offence to make it easier to prosecute British citizens who hold undisclosed money in offshore accounts.
The changes would give HM Revenue & Customs the power to prosecute people who do not declare their foreign income, even if they do not deliberately intend to avoid payment.