Environment Minister Mark H Durkan has vowed to keep 300 Driver and Vehicle Agency (DVA) jobs in Northern Ireland.
Mr Durkan was speaking as a public consultation process into whether DVA services should be centralised in Swansea, Wales, ended on Wednesday.
In December 2011, the Department for Transport in Westminster proposed the closure of 39 regional offices in favour of the Swansea centralisation, claiming the move would save tax payers millions of pounds.
DVA staff based in at County Hall, Coleraine, expect to hear an outcome to the consultation within 90 days.
Speaking at County Hall, Mr Durkan said he was demanding a meeting with Transport Secretary Stephen Hammond before a decision is made.
"I dispute that it is a done deal," he said. "I have already written to MPs, I've written to every MLA, I've been assured of cross-party support and I believe that the Assembly has to take this battle to the highest level and if that means OFMDFM going to the prime minister that is what needs to be done.
"It's important that we don't lose this fight – it's a fight that we are united on."
The SDLP MLA for Foyle said that he had unanimous backing from MLAs right across the political spectrum.
John Dallat, SDLP MLA for the East Londonderry constituency, said: "I hope this is the beginning of the political campaign to save the 300 jobs in County Hall.
"From today on, the politicians will take over from the consultation and we are united in our determination to ensure that these jobs are not going out of Coleraine to Swansea."