Austria, which does not have nuclear power, has said that the appeal will be launched by April and could delay a final investment decision by the UK government for over two years.
The Austrian government has the unanimous support of Austria's parliament.
The lawsuit - targeted against the EU’s state aid approval - will be filed after publication of the commission’s decision on Hinkley in the Official Journal of the EU, which is expected in the next fortnight.
Britain’s Guardian newspaper reports that Luxembourg is very likely to support the case in the European court of justice, arguing that the UK’s loan guarantees constitute illegal state aid.
"Austria strictly rejects any kind of direct or indirect subsidies to nuclear power, arguing for the complete internalisation of all external costs based on the polluter pays principle," a spokeswoman for Austria’s environment ministry told Interfax Energy.
"Austria also does not consider nuclear power to be eligible for the European Fund for Strategic Investments [EFSI]," she added.
The EFSI is a €315 billion ($372 billion) package promoted by the new commission, led by Jean-Claude Juncker, that also will invest in energy infrastructure projects.
Austria does not consider nuclear power to be a sustainable form of technology, neither in environmental nor in economic terms, and the environment minister has called it "stone age technology".
Work has already begun at the Hinkley site in Somerset. It is being built by France's EDF at a cost of €19 billion.
Austria’s environment ministry estimates that a European court case could last around two years.