HM Revenue & Customs has denied letters sent to tens of thousands of people with overseas bank accounts and investments constitute "bullying".
Letters from the Risk and Intelligence Service have been sent out that state: "We have information which shows that you may have received overseas income or gains which is taxable in the UK.
"It is your responsibility to tell us about your UK tax liabilities from offshore income or gains anywhere in the world."
HMRC noted the wording in the letters does not represent a substantial amendment to any communications the tax office has previously sent out.
But an article in The Times claimed the tone of the letters amounted to "bullying" – an accusation HMRC strenuously denied.
A spokesman for HMRC said these were standard letters and they were just to flag to people with offshore accounts that they need to get their complex tax affairs right.
The spokesman said: "We are writing to customers where HMRC has information that shows they have an account or investment overseas.
"This information can come from the Common Reporting Standard and/or other international agreements to automatically exchange data.
"We are asking them to check their tax affairs are up to date as we know offshore tax can be complex. HMRC’s approach to compliance is to support people to comply with their UK tax liabilities and focus our investigative resource on the non-compliant.
"If they are unsure their tax affairs are up to date, we suggest they seek advice from a tax professional and make a disclosure using the Worldwide Disclosure Facility where they need to bring their tax affairs up to date.
"We are not saying that they have done anything wrong. This activity is about helping people with complex tax affairs to check that they have paid the right amount of tax at the right time."
International tax lawyer Miles Dean, managing partner of Milestone International Tax, agreed the letters simply amounted to the tax officers doing their jobs.
He said: "The fact of the matter is that HMRC has an obligation to collect all taxes due – they have a responsibility to write letters about individuals’ personal finances.
"The letters do not state that the individuals have either avoided or evaded UK tax, merely that HMRC has information about overseas income that may be taxable.
"The reality is that with automatic exchange of information now being a global standard, and the breadth of the UK tax code, taxpayers can't assume they won't get letters such as this in the future."