Opposition leader Tony Abbott appears to be trying to trump Prime Minister Julia Gillard on the issue of mental health, which is expected to feature in the federal government's May budget.
The opposition leader will announce more than $400 million worth of mental health initiatives during a speech to the University of Sydney's Brain and Mind Institute on Thursday.
The commitment comes amid growing speculation that mental health will feature in the budget.
The Ten Network on Wednesday reported that mental health will be the centrepiece spend.
Mr Abbott accused Labor of neglecting mental health, an area it promised to prioritise.
"The coalition will hold the government to account for any further neglect, while indicating what we would do should the grave responsibilities of government fall to us," he said.
That includes extra money for employment services for people with serious mental health problems, a new research centre and mental health commission.
The commission will provide expert advice to a dedicated minister for mental health - another commitment the opposition leader will outline during his speech.
The new initiatives come on top of the coalition's $1.5 billion election promise to deliver 800 extra mental health beds and 80 intervention centres.
The coalition's criticism of the government has been backed by online action group GetUp!.
The organisation publicly questioned the federal government's commitment to fund mental health on Wednesday through a full-page advertisement in The Australian newspaper.
Acting prime minister Wayne Swan has defended the government's record in response to the ad, which included a petition signed by more than 100,000 GetUp! members.
Mental health is a "very significant priority" for the government, he said during his pre-budget address at the Queensland Press Club.
The coalition won't deliver on spending promises, he said, arguing it could not deliver a budget surplus.