The London-based Metropolitan Police Sikh Association has accused the Garda Síochána of "racial discrimination" for refusing to allow a Sikh recruit to wear a turban as part of his uniform.
The association says Sikhs have been wearing turbans as part of the uniform of the Metropolitan Police since the early 1970s, reflecting the wider community the force serves.
"Ireland's police force is 40 years behind the Metropolitan Police Service and the other civilised countries that recognise that Sikhs need to wear their turbans as part of their religion whilst officiating in public roles," the group said.
"Such decisions by the Garda do not support community cohesion, diversity, tolerance of other faiths and pluralism. Unless this decision is reversed, the Sikh community of Ireland will enjoy no confidence in their police force, and An Garda Síochána will find it difficult to recruit Sikhs into the force for years to come."
The association said the Garda's position had echoes of religious intolerance in some parts of the Middle East. It was also concerned at the Government's apparent support for the Garda's stance.
"We are dismayed to learn that Ireland's police force has racially discriminated against the Sikhs in their refusal to allow a Sikh officer to wear a turban as part of his police uniform," the group said. "Equally disconcerting is the fact that the Minister for Integration has allowed this to happen. The question is not one of cultural integration, rather of religious rights and freedom to practise an individual's faith, regardless of jurisdiction."
The Minister of State with responsibility for integration, Conor Lenihan, said last week that foreign nationals coming to Ireland needed to understand the ways things were done in Ireland.
"When the President and ministers travel to the Middle East, they accept cultural requirements of the country and the culture they are operating in. It is a vice-versa situation with regard to Ireland."
A Garda spokesman defended its decision and said all members were required to wear standard-issue uniform when on operational duties.
The Irish Sikh Council has criticised the decision and said police forces and armies in other countries such as Britain, the US, Singapore, Malaysia, Pakistan and India allowed members to wear turbans.