People are being urged to hang up the phone if they receive an automated voice call from HMRC which threatens them with legal prosecution.
The phone calls are telling victims they are under surveillance and have to call the HMRC on a 0333 number.
The automated voice says: 'Hi. We are calling you from the legal department of Her Majesty's Revenue and Customs.
'The reason of this call is to make you aware that we have received a legal lawsuit against your name where you are being listed as a primary suspect for the case being filed against your name and your house is under surveillance so do not disregard this message and call us back on 0333 344 1463.
'Remember delay in calling us back may end in legal prosecution for you. Thank you.'
Both HMRC and Action Fraud are aware of this type of scam - which targets older people in particular - and are urging victims to end such calls immediately.
A spokesperson for Action Fraud said: 'We are warning of fraudsters who contact victims claiming to be from HM Revenue & Customs (HMRC) to trick them into paying bogus debts and taxes.
'This type of contact is designed to convince you to hand over valuable personal details or your money.
'Don't assume anyone who has contacted you is who they say they are. If an email, phone call or text message asks you to make a payment, log in to an online account or offers you a deal, be cautious and report it to Action Fraud online or call 0300 123 2040.'
In a statement on their website HMRC said: 'HMRC is aware of an automated phone call scam which states that HMRC is filing a lawsuit against the recipient of the call and states they should '˜press 1 to speak to a caseworker in order to make an immediate payment'. We can confirm that this is a scam and you should end the call immediately.
'This scam has been widely reported, and appears to be targeting elderly and vulnerable people.'
Any contact from HMRC will always include the unique taxpayer reference number.