The DUP has pledged to block plans by Regional Development Minister Conor Murphy to provide for Irish language and Ulster-Scots road signs.
The Sinn Fein minister announced a public consultation on allowing council welcome signs in towns or villages, plus signs at schools or tourist sites, to be in English as well as either Irish or Ulster-Scots.
But the DUP objected and claimed councils already had similar powers, accusing the minister of seeking to extend it to other sites.
Mr Murphy said the measure would help his department meet commitments under the European Charter for Regional or Minority Languages.
"The policy is intended to facilitate the introduction of a number of certain bilingual traffic signs in Irish or Ulster-Scots for the specific purpose of promoting minority languages," he said.
"We have obligations under the European Charter for the protection of minority languages and the proposed policy will permit the inclusion of either Irish or Ulster-Scots, on town or village welcome signs, some supplementary plate signs, for example a 'School' warning sign, and certain tourist signs."
Bilingual signs would have to be requested through a local district council and any costs would be borne by the applicant, which may be a council or, in the case of a tourist venue or a school, an individual.
DUP deputy chair of the Assembly's Regional Development Committee Michelle McIlveen criticised the plan and said the minister knew it would not be supported by the DUP at Executive level.
"Given the range of problems on Conor Murphy's desk he should be focusing on more important matters rather than a pointless political exercise about bilingual signage," she said.
But Sinn Fein language spokesperson Pat Sheehan welcomed the move, saying: "It is another step in the right direction in meeting the Executive commitments under the European Charter for the protection of minority languages and I am glad the Regional Development Minister has brought this forward for discussion."