Speaking during prime minister's questions at the House of Commons, Clegg said that one-in-four people faced mental health problems, and that millions have to wait for three years to get help.
He asked Brown to acknowledge "that we now have a two-tier health system in which millions of mental health patients are being left behind".
The prime minister said the government had increased spending on mental health by 31 per cent in real terms in the last 10 years.
This had funded 60 per cent more consultant psychiatrists and 20 per cent more mental health nurses, he said.
He added: "That is only possible because of the investment we have made in the National Health Service, which is far beyond what many of the other parties offered or promised at any election.
"That is why there are 80,000 more nurses, that is why we're doing a billion more operations and that is why today this party, and I believe the whole House should be proud of 60 years of success of the National Health Service.
"I am proud it was a Labour government that created it. I hope it will have the support of all parties in this House."
Clegg accused Brown of "confusing a list with an answer, confusing a review with action".
"There is a mental health crisis in this country today," he said.
And he pointed to comments from the president of Royal College of Psychiatrists who said that mental health wards are "unacceptable, uninhabitable and dangerous".
"There is no excuse for the prime minister's complacency," Clegg said. "He once again relies on a promise made in a review. But when will he act to introduce a maximum waiting time and equal rights for all mental health patients?"
Brown said that government policy aimed to increase the levels of care in community, adding that "real investment" in adult mental health had increased by £1.2bn, with over £5.1bn spent on adult mental health last year compared to £3bn in 2001.
"Yes we want to do more, but we can only do more if we invest more in the National Health Service as a whole," he said.
"That is our commitment. It's not clear it's the commitment of all parties in this House."