Vodafone currently offers the lowest “fair usage” costs for mobile customers using data in Europe amid ongoing uncertainty about whether all four major UK providers will eventually reintroduce roaming charges.

EE became the first to bring back roaming charges last month when it announced that new customers and those upgrading contracts will have to pay to use data on smartphones when travelling on the continent from January 2022.

The surprise move prompted consumer champion Which? to appeal to the UK and EU to come up with new rules that would prevent operators from “chipping away” at the benefits that customers had become accustomed to.

Roaming charges had been abolished in 2017, but the Brexit trade deal signed in late 2020 opened up the possibility of them returning.

This is because it did not explicitly rule out roaming rates and instead urged operators to provide “transparent and reasonable” fees.

EE broke ranks to reintroduce them in June, but Three, O2 and Vodafone have not joined them yet.

However, there are already fair usage limits in place that could lead to customers racking up costly surcharges.

EE will be the most expensive from January when customers will have to pay a flat-rate of £2 per day or £10 per month for an add-on to roam in Europe.

The other networks currently have no plans to charge for roaming but Three does not allow customers to exceed a fair usage limit of 12GB, while O2 incurs a charge of £3.50 per 1GB over 25GB.

Vodafone is the cheapest, but only just, with its £3.13 per 1GB charge for data over 25GB.