Portugal's border agency SEF has faced criticism for delays in issuing post-Brexit ID cards to thousands of British nationals in the country, putting the spotlight on a structural problem that has affected various other migrant communities for years.

Nearly 35,000 British nationals called Portugal their home in 2019, the year before Britain left the European Union (EU), and, as part of the withdrawal agreement, their rights were to be safeguarded.

They were told by SEF to exchange their EU residence permits for biometric ID cards, but the vast majority have not received those cards and were only given a temporary document and a QR code, which campaign groups claim are not widely recognised.

Tig James, co-president of British in Portugal, said without the card people have struggled to access healthcare, exchange their driving licence, get jobs and some have even been threatened with refusal of entry into Portugal because other EU nations do not accept the temporary document.

James said SEF officials have cited staff shortages, holiday periods, COVID-19 and the arrival of Ukrainian refugees to justify the three-year delay.

"The seriousness (of not having the card)... cannot be underestimated, it has paralysed and damaged UK nationals... emotionally, physically and financially," James said.

In a statement SEF said the temporary document and the QR code guaranteed access to health and social services and would be accepted until the card was issued. It said other European countries were aware of it.

The issuing of the cards started in February on the islands of Azores and Madeira, where fewer than 1,500 British people live, and SEF said it would start the process in the seaside municipality of Cascais, near Lisbon, this month.

SEF did not reply to a question on how many cards have been issued so far.

For years the SEF has been accused of being too slow and inefficient, with the organisation Diaspora, which mostly supports migrants from Brazil and the African continent, saying on average people wait two to three years to get an appointment.

Helena Schmitz, from Diaspora, said the waiting time brought "insecurity and instability" to migrants' lives, who often have to work precarious jobs and fear filing discrimination complaints due to lack of ID documents.

"It is much deeper than simply not having a residence permit," Schmitz told Reuters, adding that "privileged groups" often have more access to SEF because they can pay for lawyers to take care of the process.