With the summer holidays upon us we have had a flurry of complaints from readers who have fallen for copycat websites that aim to dupe those applying for an Esta permit (the US’s online visa system) and, to a lesser extent, the Ehic health insurance card into paying unnecessary fees.

Under the terms of the Visa Waiver Program, all Britons entering the US are required to apply online at esta.cbp.dhs.gov/esta, at least 72 hours prior to travel and pay a $14 (£10.60) fee. From April this year, they also need to hold a biometric passport with a built-in chip.

However, unscrupulous operators have set up copycat websites, where the sole purpose seems to be to catch out the unwary and get them to hand over an additional service or administration fee. They do so by making their website look like the official site, or by just hoping that some consumers don’t know better and will pay them for the unnecessary service.

Guardian Money has repeatedly warned about this issue, but despite moves by Google and promises of action by UK ministers, it shows no sign of going away. There is even a warning about fake sites on the official Esta site.

The free Ehic card gives access to state-provided healthcare during a temporary stay in another European Economic Area country and Switzerland. Although the service, at gov.uk/european-health-insurance-card, was temporarily unavailable online immediately after the result of the Brexit referendum due to a technical glitch, it is now up and running as normal.

Copycat websites still provide the Ehic card, but charge an unnecessary fee. We have learned of a spate of “reminder” emails being sent to consumers who have already been duped into paying fees as their cards get close to expiry. You have been warned.

We welcome letters but cannot answer individually. Email us at consumer.champions@theguardian.com or write to Consumer Champions, Money, the Guardian, 90 York Way, London N1 9GU. Please include a daytime phone number