British expatriates residing in Spain said on Sunday they were prevented from boarding flights to Barcelona and Madrid after airlines claimed their papers were no longer valid post-Brexit.

Photographer Max Duncan, one of those who said he was turned away at Heathrow Airport on Saturday, tweeted that several British expats were "distressed as (they) can't fly home", having been told their green residence certificates were no longer valid.

The British embassy in Madrid responded that "this should not be happening," adding that the Spanish authorities had confirmed that the green residency document was valid for travel.

Spain's foreign ministry later confirmed that "a very small number of travellers" were affected by "a specific communication problem with some airlines."

"Once brought to the attention of the Spanish authorities, it was corrected immediately, and today air traffic between the United Kingdom and Spain flows normally," added the spokeswoman.

The British and Spanish governments had advised that both the old Foreign National Identification (NIE) document and the new Foreign ID Card (TIE) are valid for travel.

Another traveller tweeted Sunday that they were refused boarding by BA at Heathrow as officials in Barcelona were not accepting the NIE, adding that around ten passengers had the same problem.

Madrid announced last year that post-Brexit, British nationals resident in Spain would be given a photo ID to replace the current residency papers carried by EU nationals.

Tens of thousands have applied for the card, but many are waiting to receive them due to demand on the system.

Spain restricted passenger travel from Britain on December 22 due to the rapid spread of a new coronavirus strain identified in the UK, with exceptions for Spanish nationals and those legally resident in Spain.

There are believed to be around 300,000 Britons currently living in Spain.

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