Tory MPs have rallied behind Theresa May’s battle line on travel, challenging the Government’s apparent "zero Covid" strategy.

Up to 40 Tories – potentially sufficient to overturn the Government’s majority – are thought to be unhappy with ministers’ reluctance to take advantage of the UK’s successful vaccination programme to reopen foreign travel.

Mrs May opened the attack in a Commons debate on the travel industry on Thursday when she said Britain was "shut for business" because of travel restrictions that are "incomprehensible" in one of the world’s most vaccinated countries.

The former prime minister said that if ministers block travel every time there is a new variant, "we will never be able to travel abroad ever again".

Henry Smith, the Tory chairman of the Future of Aviation group, which has support from more than 100 MPs and peers, said: "I have had my differences with Theresa, but she was very eloquent yesterday.

"She is right that this is the coming battle line, whether you accept the Government’s apparent zero Covid narrative or whether you accept it is something we will have to live with for the rest of our lives and it will mutate every year."

Mr Smith has secured a second backbench debate in Westminster Hall on June 24 when the Government will face a similar backlash to Thursday’s, when a succession of Tory MPs criticised the Government’s restrictions on travel.

Only 11 countries are on the current green list allowing quarantine free travel, with just two, Iceland and Gibraltar, seen as viable holiday destinations. Portugal was removed after a rise in infections and fears over a Nepalese virus mutation.

The second debate will come just four days before the Government’s update on the green list, with Tory MPs like Mr Smith seeking a significant expansion of the list to mainland European holiday destinations and the US.

Former transport minister Stephen Hammond said: "We need to minimise Covid and then accept there isn’t a sustainable policy called zero Covid. We know from flu that there are different variants and we can vaccinate to minimise the potential harm.

"So in the light of that medical knowledge, a sensible risk-based approach and damage mitigation must be vaccination. And given the outstanding rollout of the vaccine, that route is possible and available and Government policy should reflect this."

Richard Drax, the Tory MP for South Dorset, said: "I am becoming increasingly frustrated, as are many, many people, at this Orwellian-style lockdown imposed on us when the data clearly indicates that we are on top of this pandemic.

"The traffic light system is not fit for purpose and is unreasonable in that many European countries should be on the green list."

Simon Jupp, the Tory MP for East Devon, said: "I completely agree with Theresa May. If the Governmnt isn’t going to listen to a very sensible argument to open some routes, they have to compensate the industry as a result. The amount of money being lost by airlines, regional airports and high street travel agents is dramatic."