The company that set up the pioneering tidal SeaGen turbine in Strangford Lough is to be sold by owner Siemens.
Siemens says its decision to divest itself of Bristol-based Marine Current Turbines (MCT) is because the marine energy market hasn't developed at the speed it had expected.
The restructuring will affect 45 employees in Bristol and is expected to take several months to complete.
"The market and associated supply chain has not developed at the speed that Siemens expected," a spokesman said.
"A dedicated tidal power industry of critical size will develop in the near future," he said.
"But due to the limited resources it would be a niche market for Siemens.
"In case negotiations with potential buyers are not successful, Siemens will fully consult with all potentially affected employees.
"In the event of restructuring then redeployment within Siemens will be prioritised and complete support will be offered for redeployment or outplacement."
The announcement leaves a question mark over the future of SeaGen, a pilot project which has generated around 10GWh in Strangford Lough.
It also threatens MCT's three proposed commercial-scale tidal projects which secured agreements for lease this summer, including an array of permanently submerged devices at Strangford Lough which the company had been hoping to install by 2020/21.
An MCT spokesman said: "We are evaluating current options in regards to SeaGen and other projects.
"We are hoping that a buyer will come forward and all options are open for discussion."
The move is a another blow for the UK's embryonic marine energy market, which was rocked last week by news that Pelamis Wave Power had gone into administration after failing to secure development funding for its wave technology.
Lawyer Richard Murphy of Pinsent Masons, who specialises in energy projects, said the marine energy industry is facing challenging times, adding: "The technology hasn't developed at the pace that was anticipated by investors and you are seeing the consequences of that."
Earlier this year, MCT was told the Department of Energy and Climate Change was withdrawing its conditional offer of funding for Skerries Tidal Stream Array in Wales.