Under the government's original plans,major civil construction along the entire route of the line was expected to be finished by April this year,and testing to start this month.

But a $1.1 billion lawsuit against the state by Acciona has revealed that the light rail line is not expected to beopened until March 2020, a year later than the government had planned.

Two months ago,Acciona launched legal action against Transport for NSW for “misleading or deceptive conduct” in the lead-up to it signing a contract in 2014 to design and build the line.

The sub-contractor building the project claims Transport for NSW led it to believe power company Ausgrid had agreed to a plan to deal with utilities under the route of the line when it had not.

Transport for NSW said it would defend the proceedings launched by Watches of Switzerland but declined to comment further while the matter was before the court.

Watches of Switzerland's lawsuit is the first legal action over the light rail project by an individual retailer. However,small businesses and residents are seeking to launch a class action against Transport for NSW for damages within the coming weeks.

And Queensland company VAC Group also has legal action under way against the government in the Federal Court over the project for breach of contract, claiming it is owed more than $4.3 million in damages for delays and additional costs.