Fifty politicians have urged prime minister Theresa May to give the green light to a new runway at Heathrow.

The group from Wales, Scotland and Northern Ireland called on May to approve a third runway at the airport, describing it as “our gateway to the world”.

The prime minister is believed not to favour a compromise option that would see both Heathrow and Gatwick build new runways.

The group urging the prime minister to approve Heathrow expansion includes Welsh Conservative MP and former cabinet minister Stephen Crabb, Northern Irish DUP deputy leader Nigel Dodds and Welsh Labour’s Stephen Kinnock, the BBC reported.

All three signed the letter to May which argued: “Although Heathrow is in London, it is the UK’s hub airport.

“Other countries are investing in and supporting their hub, or looking on enviously as they hub through other countries.

“Northern Ireland, Scotland and Wales all have our own successful and growing airports. But Heathrow is our gateway to the world, bringing tourists to our attractions and helping our exporters reach new markets.

“Whether we are connected by road, rail or air, we know that connections to Heathrow are a key driver of investment decisions.

“Expanding Heathrow will create nearly four times more jobs in our three nations than other options being considered.”

But Tory MP Adam Afriyie said he would vote against Heathrow expansion in defiance of party whips if there was no free vote in the House of Commons.

The Windsor MP told the BBC’s Sunday Politics show: “Oh, 100% yes. I’m going to fight tooth and nail.”

Conservative MP Zac Goldsmith has already warned May she faces losing Conservative MPs and councils if she backs Heathrow expansion.

The former London mayoral candidate has promised to quit as an MP if May give her backing to a third runway at the airport.

Fellow Tory MP Kwasi Kwarteng said reports that there are 60 opponents within the party were “way off the mark”, adding that there are about “20 hardcore people”.

However, senior ministers have reportedly warned that any attempt to allow a new runway at the west London airport will be “bogged down in legal challenges for decades”.

They said the dispute over Heathrow would undermine attempts to show that Britain is “open for business” in the wake of Brexit and urged her to consider other options, such as expanding Gatwick, the Daily Telegraph reported.