A TV licence email scam has led to more than 5,000 complaints over the past three months.
Cyber crime monitor Action Fraud said fake TV licence emails regarding payment issues had been sent out to try to collect bank details.
The number of reports has increased in each of the past three months, with 1,983 complaints in December alone.
Action Fraud told the BBC the scam was "particularly nasty as it looks so convincing".
The emails use headlines such as "correct your licensing information" and "your TV licence expires today" in an attempt to convince people to click on the link in the email.
Action Fraud said it received 5,247 complaints about such emails between 1 October and the end of December.
By comparison, there were only 1,614 complaints in the preceding nine months of the year, with the majority of those coming in September.
While the emails themselves might vary slightly in their wording, all of the links direct through to the same website.
The fake TV Licensing website asks victims to provide their payment details, including their account number, sort code, and card verification value (CVV) code on the back of their card.
The website may also ask for a victim's name, date of birth, address, phone number, email and possibly even their mother's maiden name.
Action Fraud said it was working to "stop fraudsters in their tracks".
Leesa Hellings-Lamb, from Bolton, told the BBC she received an "incredibly realistic" email from what she thought was TV Licensing claiming her licence was due to expire in two days.
She followed the link in the email and began entering her bank details but became "suspicious" when she was asked for "too much information".
"Eventually I realised it was a scam," said Ms Hellings-Lamb, who managed to avoid confirming her details to the fraudsters.
She added: "I have learnt my lesson and told everyone I know to spread the word and remind everyone to be more cautious."
A TV Licensing spokeswoman said: "TV Licensing will never email customers, unprompted, to ask for bank details, personal information or tell you that you may be entitled to a refund."
Is the TV licence email I have received a scam?
There are a number of ways to check whether or not an email you have received might be from fraudsters. Action Fraud says should check:
The sender's email address - does it look like one TV Licensing would use?
The subject line - anything such as "action required" or "security alert" should be treated with suspicion
Spelling and grammar - grammatical errors suggest it is likely to be a scam
The style - scammers often take real emails and amend them, so be wary of emails that seem too familiar or casual
The link - does it go through to the official TV Licensing website?
If you think you have received an email from fraudsters, you should report it to Action Fraud.