UP TO 300 new Brexit jobs in the UK Border Force were already filled under its 'British passports only' policy before it was abandoned over discrimination claims.
The Home Office has refused to clarify the exact number allocated using the controversial criteria, which restricted applications to only UK passport holders.
Earlier this month the department removed the requirement from its latest recruitment drive amid mounting pressure after the policy was exposed by The Irish News.
Political parties on both sides of the Irish border raised concerns, while the Equality Commission issued a warning on grounds of fair employment legislation.
The Home Office apologised and more than 1,000 posts – including 21 based in Belfast – are being re-advertised without the UK passport requirement.
It said the criteria was an "error" and application packs should simply have asked people for any valid passport.
However, before this latest intake, the Home Office had last October announced the recruitment of 300 extra Border Force staff.
The recruitment took place at the end of last year. Some application packs still available online state that candidates needed a "full and valid British passport".
Among those who applied during this earlier recruitment drive was a Belfast woman working as a police officer in England.
She told The Irish News how the Border Force refused to accept her job application for a Northern Ireland-based post – despite her querying the UK passport requirement and even citing the Good Friday Agreement.
The Home Office was asked to clarify how many new Border Force posts were already filled under the 'UK passports only' criteria before it was dropped, but it did not respond.
The SDLP's Claire Hanna, the party's Brexit spokesperson, said she has been contacted by people who were unable to apply because of the passport issue.
The South Belfast MLA called on the Home Office to "clarify their position".
"The Home Office has clearly acknowledged that they were taking the wrong approach with this recent recruitment. However, if they accept that they were wrong here then they should accept that they were unfair in the previous round of recruitment as well," she said.
Solicitor Ciaran Moynagh, of McLernon Moynagh Solicitors based in Holywood and Belfast, said the Home Office could face a legal challenge.
He said unsuccessful job applicants can take discrimination cases to employment tribunals, but a complaint has to be lodged within three months unless an extension is granted.
"If the Home Office are intent on restricting roles they advertise they should properly justify the necessity for any restriction. I still have not heard that addressed in recent times," he said.
"If they do not, they could find themselves before a tribunal or subject to judicial review."
Border Force, which deals with immigration and customs checks, is advertising the new posts in preparation for the UK leaving the European Union – fuelling fears of a hard border.
The jobs are regarded as 'reserved posts', which under British government civil service rules means "only UK nationals may be employed".
The British and Irish governments and the EU all insist they want to avoid a 'hard border' on the island of Ireland.
