The council is set to recruit two new officers, one whose sole responsibility will be to promote Irish, as well as some translation and education services.
The other post will be a linguistics officer, with responsibility for Ulster-Scots and minority languages, including sign language.
The move, which was approved by the council’s strategic policy and resources committee on Friday, comes after a public consultation showed majority support for the creation of both posts.
Unionist parties on the council objected and instead wanted one officer to take responsibility for all languages, including Irish.
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DUP councillor Lee Reynolds said the decision to hire an officer to focus on Irish “just doesn’t make sense”.
He added: “It beggars belief that one officer will be tasked with looking after Irish, while the other will have to deal with all the rest.
“It is not a balanced approach. We had proposed that one linguistics officer would have been a more appropriate use of ratepayers’ money.”
Mr Reynolds said there has never been any statistical evidence to justify the creation of the post.
“There is very little demand for council services in Irish,” he added.
“While the public consultation showed there was a desire for such a post from some quarters, that does not mean there is a need for it.”
He claimed the decision to appoint an Irish language officer was “not about good policy”, adding: “It is about some parties using the issue of Irish language as a political totem.”
Welcoming the council’s decision, Alliance councillor Michael Long said: “We have listened to what the people of Belfast have said and it’s quite clear – they want to have an Irish language officer, along with an additional officer for other languages. Alliance is happy to support that.”
But Mr Reynolds said Alliance’s position was further evidence of the party’s “love-in” with Sinn Fein.
The decision is subject to ratification at the next meeting of Belfast City Council.