Construction has begun on a new acute mental health facility in Melbourne.

Premier Daniel Andrews and his deputy James Merlino visited the site of the 22-bed facility at the Royal Melbourne Hospital on Thursday.

The new beds have been designed in consultation with people who have lived experience of the mental health system, including patients, carers and staff.

Royal Melbourne Hospital chief executive Christine Kilpatrick said the facility would provide a safe, peaceful and calming environment for Victorians experiencing acute mental health concerns.

"It's substantially different to what we have at the moment," she told reporters.

Mr Andrews said once completed in 2024, the facility will support an extra 488 Victorians to get the care they need each year.

Last year, the Victorian government committed $492 million to deliver 144 new mental health beds, as recommended by a royal commission into the sector.

The government has also committed $18 million to support 132 new junior doctors to undertake a psychiatry round in 2022, which will help address the workforce shortage in the sector.

"We know our mental health system has to grow to care for every Victorian who needs it," Mr Andrews said.

"That's why we're not wasting a moment in delivering the royal commission's recommendations - because lives depend on it."

Opposition spokeswoman for mental health Emma Kealy said the commitments made by the government on Thursday were both long overdue.

Ms Kealy said the commission's interim report, released in November 2019, recommended a proportion of junior doctors undertake a psychiatry round from 2021.

It recommended the round become mandatory for all junior doctors "by 2023 or earlier".

She said figures provided by the health departments shows just 29 junior doctors - or 32 per cent - will undertake the rotation in 2021-22.

"Years of Labor delays is nothing to celebrate, particularly given the skyrocketing demand for mental health support from Victorians during the pandemic - and the lack of resourcing from the state to meet the demand," Ms Kealy said in a statement.

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