The Transport Salaried Staffs' Association (TSSA) has called on the government to keep HS2 within the public sector.
Welcoming the recent publication of its Hybrid Bill, the union's leader Manuel Cortes stated the line should stay public, with affordable fares. Privatisation, he argues, would turn the service into a "rich man's toy".
He said: "If we are serious about ending the north-south divide, it should be kept in the public sector for the benefit of the public who will pay to build it."
While selling off contracts could cause problems and a possible public backlash, seen in the government's recent attempts to privatise the East Coast Main line, doing so could possibly reduce the costs of the scheme.
If private firms were contracted into the construction or funding of HS2, this could cut down on the £50 billion in expenses, an area which is a key factor among those both for and against the scheme.
Nonetheless, Mr Cortes said the service was vital for both environmental reasons and helping to avoid overcrowding on the current rail network.