According to The Guardian, "gaps" in the UK government’s application to Brussels have led to the delay.

Approval would see the information held on the NHS app automatically recognised across the EU’s 27 member states allowing travel and access to hospitality venues where vaccine proof is required.

The UK government applied to link up to the EU’s digital certificate on 28 July, The Guardian reports, but the European Commission has reportedly held off from giving approval until it receives "extra technical information" from Whitehall.

According to recent government advice, Hungary will only accept a locally issued immunity certificates as proof of vaccine status from the UK.

Britons in Italy, meanwhile, have reported problems entering bars and restaurants using the NHS Covid pass, while those travelling to Latvia and Croatia claim to have been told they need a paper certificate.

However, at least 19 EU member states – including France and Spain – have unilaterally accepted the NHS app as proof of vaccination.

A UK government spokesperson told The Guardian: "We have applied to link into the EU’s digital Covid certificate (DCC) scheme. We expect the EU’s technical assessment of our DCC application to take a few weeks, as was the case with Switzerland and other states.

"We have had good technical exchanges with the EU commission concerning our application. While the application is considered, member states are still able to decide individually to accept UK Covid certificates."