Fraudsters have been contacting victims with a landline number claiming to be from HM Revenue and Customs, as the tax authority warned the more traditional method of scamming was making a return.
HMRC warned phone scams were being used to target the elderly and vulnerable, using its brand to threaten legal action or prison to encourage payments from victims.
Following a crack down on email and SMS phishing in recent years, the government has seen a rise in the number of fraudsters turning to the more traditional method of cold-calling publicly available phone numbers to target taxpayers.
HMRC received more than 60,000 reports of phone scams in the six months leading to January 2019, an increase of 360 per cent compared to the previous six months.
In the last 12 months HMRC, in partnership with phone networks and Ofcom, closed almost 450 telephone lines used by fraudsters using high-pressure tactics to steal money from victims.
Mel Stride MP, financial secretary to the Treasury, said: "We have taken major steps to crackdown on text and email phishing scams leaving fraudsters no choice but to try and con taxpayers over the phone.
"If you receive a suspicious call to your landline from someone purporting to be from HMRC which threatens legal action, to put you in jail, or payment using vouchers: hang-up and report it to HMRC who can work to take them off the network."
Pauline Smith, head of Action Fraud, said: "Fraudsters will call your landline claiming to be from reputable organisations such as HMR - contact like this is designed to convince you to hand over valuable personal details or your money.
"Don’t assume anyone who calls you is who they say they are. If a person calls and asks you to make a payment, log in to an online account or offers you a deal, be cautious and seek advice."
HMRC warned it will only call taxpayers asking for payment on a debt they are already aware of, either having received a letter about it or if the taxpayer has already declared tax owed through a self-assessment return.