Concerns over 'copycat websites'
The advertising watchdog has received hundreds of complaints about "copycat websites" that charge for services that are available free.
A number of websites that offer assistance in updating a driving licence or completing a tax return are found during online searches.
The Advertising Standards Authority said it had received 700 complaints about 25 websites in the past year.
But one website hit back, saying it was upfront about the service and charges.
Part-time nurse Vanessa Andreae thought she was taking the easy option when she decided to file her tax return using what she believed was an official website.
She was charged £400 to file her return by the taxreturngateway.com website. Only later did she realise she could have filed her tax return free through the official HM Revenue & Customs website.
"They do say in quite small print at the bottom of the screen that they are not HMRC, and here's a link to go to the HMRC," she said. "But if you are someone who is in a bit of a flap, trying to get it done with children and life going on around you, you tend not to read the small print.
"It does say you accept terms and conditions, which I completely admit that I did. Nobody held a gun to my head and made me fill out that site. I just did it because I had absolutely no idea that there was a wrong way to do it and a free way."
She hoped that her experience would prove to be a warning to others. She has since got her money back and the website she used has been upgraded.
In a statement to the BBC, taxreturngateway.com said: "We do not accept the suggestion that we are a copycat website. We are a bespoke tax return checking and fulfilment agency.
"We have always made it absolutely clear on the homepage of our website that we are not associated with HMRC, Department for Work and Pensions or any other government body, and that we will levy a charge for the service we provide."
These websites are perfectly legal and many do make it quite clear that they are providing a service that the user will have to pay for. Some of the sites look very similar to official ones and some people might not read through the disclaimers or the terms and conditions.
Many of these websites are paying for sponsorship on search engines such as Google and therefore appear at the top of an online search.
The Advertising Standards Authority said it had received around 700 complaints in the past 12 months about transparency and pricing.
"Complaints that we are receiving are about people being misled as to the nature of the service being offered, a feeling that they might be official services when actually they are not," said the ASA director of advertising policy and practice, Shahriar Coupal.
"Perhaps a little bit more worrying [are concerns] about the pricing or the transparency of the pricing - people feeling that they are left out of pocket for a service they would not have entered into had they known that it wasn't official."
Commentators say there are ways to avoid these websites.
Sarah Pennells, editor of Savvywoman.co.uk, said that people should search for services such as passport and driving licence renewal within the official www.gov.uk website.
"If you do just type the search term into the search engine and you're not quite sure where you have ended up, just check what you are being charged for and then do another search and see whether you can get this for free," she said.
The ASA and Google said they were working closely with government digital services to ensure adverts were not misleading.
Google said in a statement: "We have a strict set of policies which govern what types of ads appear on Google. If we learn an advertiser is breaching these policies, we move swiftly to take action."