Transport Minister Andrew Constance has turned up the heat on Spanish construction company Acciona to complete Sydney's bungled $2.1 billion light rail line early next year by insisting the remaining work is relatively minor and straightforward.

Returning fire a week after Acciona fronted an inquiry into a project which has become a political liability for the government, Mr Constance said there was “not actually too much left” of the civil construction to finish but the contractor had a lack of people working on it.

Transport Minister Andrew Constance says Acciona should finish the light rail line by early next year. Credit:David Porter

“There's no doubt that on the basis of what's left, it should be done by the first quarter of next year. And that's where that May 2020 date starts to come a little bit laughable, and I believe is designed to anger and in many ways frustrate the community,” he said.

Acciona warned last week at the parliamentary inquiry that the 12-kilometre line is now unlikely to be opened until May 2020 – 14 months later than the original schedule – because power company Ausgrid needs to shift overhead lines at Kensington and Kingsford.