The Government could have changed the colour of British passports back to blue at any time regardless of Brexit, it has emerged.

Theresa May described the decision to revert to the “iconic” colour as an “expression of our independence and sovereignty” away from the EU.

But the Home Office confirmed that the UK voluntarily adopted common passport criteria from the European Economic Community (EEC) and was not obliged to keep it.

The guidance states that the cover of member states’ passports should be “burgundy red” and stipulated features including the number of pages and information that must be included.

An EEC resolution drawn up in the 1970s hoped the move would “strengthen the feeling among nationals of the member states that they belong to the same community” and facilitate their movement.

A Government source told The Independent the agreement was not legally binding and that redesigns have been considered around every five years.

“But changing to blue would have looked odd, whereas now it doesn’t look that odd,” he added.

Croatia notably refused to change the dark blue colour of its passports after joining the EU in 2013, with the interior minister telling local media: “The EU’s position is that there is no obligation.”

Britain’s previous blue colour was itself a foreign imposition, originating in guidance issued by the League of Nations in 1920 – which also stipulated French must be included – and the UK has introduced some biometric features to comply with American visa waiver requirements.

The new design will be phased in once Brexit comes into force in 2019, no longer including the EU insignia.

Brandon Lewis, a Home Office minister, said the new passport will be the “most high-tech and secure we have ever seen” and be more resistant to fraud and forgery.

“Leaving the EU gives us a unique opportunity to restore our national identity and forge a new path for ourselves in the world,” he added.

“That is why I am delighted to announce that the British passport will be returning to the iconic blue and gold design after we have left the European Union in 2019.”

A £490m contract to produce a new version of the document was announced earlier this year but the shift to blue has largely been seen as a move to appease Eurosceptics amid floundering Brexit negotiations.

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

Nigel Farage was among those celebrating the change, tweeting: “Happy Brexmas!” He added: “In the 2016 referendum, we wanted our passports back. Now we’ve got them back!”

But Remain-supporting Conservative MP Anna Soubry was more sceptical.

“Not sure they’ll make up for broken Leave promise of extra £350m a week for NHS,” she tweeted.

Neil Coyle, the Labour MP for Bermondsey and Old Southwark, commented: “A new passport that makes holidays more expensive, limits where people can work or study & costs billions.”

Many British passport holders born after 1988 took to social media to point out that they never owned the old passport.