The government has previously paid rental assistance to businesses with up to 20 full-time equivalent employees and will expand that to those with 50 workers.

Mr Constance said the rental assistance would continue until the end of major civil construction.

However, with the government locked in a $1.1 billion dispute with Spanish subcontractor Acciona, the completion date is not certain.

The light rail, running from the CBD to the eastern suburbs, was meant to be finished in 2019 but Mr Constance was advised by contractor ALTRAC in April the new completion date was March 2020.

The light rail was originally budgeted to cost $1.6 billion before a $500 million blowout.

Acciona's new demands threaten to double the original cost.

Stores along the light rail route have criticised the government for not doing enough to compensate them for the loss of business caused by the prolonged construction works.

"They are crushing us," one business owner told AAP in April upon learning of the fresh delays.

"We're an established business and can weather the storm but the mum and dad businesses, the small restaurants, they're being swallowed up by this."

Australian Associated Press