Feeling the heat: David Cameron last week in Lanzarote

The network already offers the service in 16 countries including France and the US

Three is to give free roaming to customers travelling to Spain and New Zealand, as part of its Feel At Home plan.

The plan allows people to use their phones at no extra cost in foreign countries. It is already available in 16 countries including France, the USA, Australia and Italy.

Those on the Three network can use their plan as normal, making phone calls and texts as well as using the internet as part of their normal alliances. Tethering is not included in the plan.

Spain and New Zealand will join the plan from April 1, 2015. The company said that it had introduced the new plan in advance of the summer holidays, when more than 13 million people are set to head to Spain. Around two million holidays will be booked in January.

About 49% of Three customers' trips abroad are to destinations that are part of the Feel At Home plan, said Dave Dyson, CEO of Three. Spain and New Zealand will take that to roughly 65%, he said.

The company will continue to add new countries to the plan, it said.

It is already available in France, Switzerland, Israel, Finland, Norway, USA, Indonesia, Sri Lanka, Macau, Australia, Italy, Austria, Hong Kong, Sweden, Denmark and Republic of Ireland.

To make use of the service, Three customers can just turn their phone on in the country they've travelled to. The phone should register to a local network and notifications should come through to confirm that it's in place.