Nick Clegg called the Liberal Democrat manifesto "an insurance policy against a government lurching off to the extremes" after the election.
The Lib Dems have pledged to increase funding for education from "cradle to college", which they claim will mean spending £5 billion a year more than the Tories and £2.5 billion more than Labour by 2020.
Nick Clegg has reiterated that mental health care is a priority in the Liberal Democrat election manifesto.
"We're turning the page on generations of inequality between mental health and physical health," he told an audience in Battersea during his party's manifesto launch.
A ComRes/ITV News poll suggests a huge fall in support for the party in its south-west "heartland" - with the Tories benefiting most.
The manifesto launch was held in a "creative space", a bit like a trendy bar. But this is serious stuff though.
The Lib Dem 'cradle to college' pledge and theme of "opportunity" is one of of five policies featured on the front of the party's manifesto.