A British woman from Aberdeen and her 11-month-old baby have been stranded abroad because of new rules regarding dual nationals introduced by Labour.

Sarah Schloegl was refused board on a Ryanair flight from Alicante last week after she went to Spain for a short break with her Austrian husband, Philipp, their three-year-old daughter and 11-month-old baby.

Since February, British dual-nationals have had to show a British passport or a certificate of entitlement of abode, costing £589, when they board flights, trains or ferries to the UK.

Schloegl said she followed the news but was unaware of this change and argued it should have been displayed on posters in airports and on airline websites months before the change, so passengers did not fall foul of the rule on return journeys.

The first she knew of the rule change was when she got to the departure gate in Alicante. Her older child, who has Austrian and British passports, and her husband, who has post-Brexit settled status, were told they could board the Ryanair flight, but the baby was refused.

“I do feel this is ridiculous, because my baby was born in the UK, lives in the UK, but she’s not allowed to enter the UK, even with me, her mum, who is British,” said Schloegl. “I’m from Scotland, our two kids were both born in Scotland, my parents, grandparents are all from Scotland and my husband has settled status.

“If you think about this, who are the most affected? It is probably kids and young people are probably the ones who, with dual nationality, who are impacted most,” Sarah said.

She, like hundreds of others who have contacted the Guardian in the last two months, have complained that the Home Office did not communicate the rule change effectively, something the immigration minister, Mike Tapp, has previously dismissed as “absurd”.

“The Home Office said they would take a compassionate and pragmatic approach to travellers who experience genuine difficulty,” said Monique Hawkins, head of policy and advocacy at the campaign group the3million. “We cannot see the compassion in refusing boarding to an 11-month baby.”

While the Home Office has said the information was on gov.uk, dual nationals say nobody looks at the site.

Sarah said she was aware of the new Electronic Travel Authorisation (ETA) – which her Austrian in-laws need to enter the UK – because it was displayed on airline websites and had been widely publicised, but the rule on dual nationals had not.

The lack of communication has seen Britons living abroad, sometimes for decades, miss important family occasions including funerals and visits to elderly parents.

Schloegl said the ground staff were helpful and directed them the airport’s help desk in the hope they could board a later flight. “When we spoke to them we also phoned the registry office back home and they sent a scanned copy of the baby’s birth certificate which tells you she was born in the UK and that her Austrian passport was issued to her by the Austrian embassy in the UK.

“They seemed to think that would be enough proof that she was British, but when they spoke to the Home Office they were told: ‘No, she’s not allowed into the country,’” said Schloegl.

She was subsequently refused emergency travel documents for her baby, and was told by the British embassy in Spain that she did not meet the criteria for the special papers.

The group has written to the European affairs minister, Nick Thomas-Symonds, and the European Commission head of trade and economic security, Maroš Šefčovič, calling for action on dual national children of those with settled status.

They want the implementation of the Brexit withdrawal agreement to ostensibly cover children who become dual British nationals at birth due to a parent being British or settled in the UK.