A London-based charity worker, who was denied boarding a Ryanair flight while on a work trip to Montenegro, has accused airport staff of “racism” and “making up their own immigration rules as they go along”.

Neha Kagal, who has an Indian passport and a British visa and residence permit, says she was left angry and humiliated after boarding staff at Stansted airport refused to let her enter the flight last March on the basis that she did not have a visa for the Schengen area of Europe.

Her case is the latest example of airlines wrongly banning people from flights to avoid potential fines from the destination country.

The Embassy of Montenegro in London had categorically told Kagal that she didn’t need a Schengen visa – and has since confirmed this in writing – but ground handling staff refused to listen.

She says she and a colleague were forced to stand aside as other passengers were allowed to board. To compound their frustration, she claims airport staff told her that they had to be very “wary of people with blue (Indian) passports” and told her that it didn’t matter what the embassy said as “there was no way she was going to Montenegro on a Ryanair flight”.

She says: “Racist Ryanair apparently have their own immigration rules.”

Only after Guardian Money intervened would the airline admit it was wrong.

Kagal, who works for the UK-based Imkaan charity – dedicated to addressing violence against black and minoritised women and girls – was supposed to be flying to Montenegro with a colleague as part of a United Nations project helping these women fight sexual exploitation.

She passed through baggage check-in, where her boarding pass was stamped stating her “visa check” had been done. “But when I got to the gate they demanded to see a Schengen visa,” she says. “I told them that I had contacted the Montenegrin embassy to confirm my visa requirements. While at the airport, I even went so far as to call up the embassy to reconfirm, but the staff wouldn’t have it. It was embarrassing and humiliating.”

Given the nature of the work, the charity insists its workers only travel in pairs, so her colleague could not travel, either. The pair had booked hotel rooms, and hired interpreters, both of which had to be paid for despite their no-show.

“It was intimated that they had refused me ‘in case’ I needed to be deported back to the UK. If so, it would cost them £20,000 and so they couldn’t take the ‘risk’,” she says.

“I was to meet survivors of violence, working in very small NGOs, who had taken time out of their busy schedules to meet with us. In the current climate of hatred and intolerance, I find the behaviour of corporations like Ryanair abhorrent and frightening.”

A Ryanair spokesperson says: “This customer was denied boarding in error by our third-party handling agent, Swissport, which has since taken necessary steps to ensure this will not reoccur. We have since contacted the customer to apologise for the confusion and inconvenience caused, and have resolved the matter directly.”

It has agreed to pay her the costs she incurred, plus €400 (£352)EU-mandated compensation, totalling £920.

Swissport tells the Guardian: “We can confirm that a passenger was held back from boarding a flight due to a staff member’s misunderstanding of the required travel documents. We take any complaints of this nature extremely seriously and are contacting the customer to apologise for the inconvenience caused. An investigation is ongoing. Staff have been briefed, and we are working to ensure processes are in place which mitigate against situations like this occurring in the future.”

More passengers grounded

In March, the Observer reported on the case of a family’s easyjet flight from Gatwick to Berlin, where the wife held a British passport and the husband, from the Middle East, had a travel document issued by the Home Office.

Easyjet refused to let the man board the flight, insisting he needed a visa to travel to Germany and refused a refund.

When shown that the visa wasn’t necessary, it then claimed to be following Gatwick procedures, but Gatwick denied this.

Only when Observer consumer champion Anna Tims intervened, and six weeks after their ordeal, did easyJet admit it was wrong, apologised and paid compensation.

Qantas banned a British couple from boarding a flight in New Zealand to Beijing in March, where they were going to stay for five nights before heading back to the UK. Check-in staff at Christchurch airport wrongly insisted that the couple needed a visa for China prior to boarding the flight.

Yet China has introduced new rules which allow travellers to go through immigration and stay in a number of cities without a visa if they can prove that they will leave China within 144 hours of arriving.