As the bank holiday season gets under way, anyone leaving the country should beware extortionate bills just for switching on their mobile phone.

Using your phone abroad to call the UK can cost up to £2 a minute, while receiving calls can cost as much as £1.50 a minute, warns website uSwitch.com.

Those with smartphones or internet-enabled handsets need to watch out for sky-high data roaming charges. These are often included in monthly packages in the UK, but can be as much as £3 per megabyte in the EU or £8 in the US.

The website’s Ernest Doku says: “One of the biggest ways to get stung is by the high cost of data roaming. Mobile internet users must ensure they check that this is turned off when not in use to prevent online services such as email updating automatically. They could also try to avoid visiting sites that are heavy on the visuals, as data is charged per megabyte downloaded – although this may be a hard ask for the Facebook and Twitter addicts amongst us.”

Four of the six main mobile providers offer bolt-on packages which give reduced rate calls, offering savings of nearly 60%. O2 customers who make just seven minutes of calls to the UK from the US would be better off buying a bolt-on.

Mr Doku said that “the minute consumers switch on their phone abroad, it will register on to a local network. This means any activity on the handset will be billed at overseas rates, which are much higher than standard charges in the UK”.