"What we actually need to see is an increase in funding," he said in response to the Prime Minister's speech detailing plans to provide greater support for those suffering mental health problems.
Van der Hart, who authored 'The Worry Book', said more cash was needed for specialist beds in young people's mental health services.
"That's not being offered in Theresa May's announcement today," he said on Premier's News Hour.
In her speech Mrs May said: "For too long mental illness has been something of a hidden injustice in our country, shrouded in a completely unacceptable stigma and dangerously disregarded as a secondary issue to physical health.
"Yet left unaddressed, it destroys lives, separates people from each other and deepens the divisions within our society. Changing this goes right to the heart of our humanity; to the heart of the kind of country we are, the attitudes we hold and the values we share."
On Premier's News Hour van der Hart said it was "always excellent to hear the prime minister talking about mental health".
He said: "I think in order to reduce stigma around mental health, we need mental health to have a greater profile, so it's really good news on that front.
"But I don't think Theresa May's actually offering us anything new here."
Mrs May admitted there were "no easy answers" to the problems, but that it was "vital" to address them.
Elsewhere Labour's shadow minister without portfolio Andrew Gywnne said mental health was a "case study in Tory failure".
"Repeatedly the Tories give speeches saying they will give mental health parity with physical health, but their record is dismal. Spending on mental health fell by £600 million in the last Parliament," he said.
Will van der Hart speaking to Premier's Alex Williams: