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 laid his cards on the table with the Liberal Democrat manifesto launch.
He said his party were vital to stop the Conservatives or Labour lurching to "extremes". He also argued a coalition including the LibDems was the only way of keeping Nigel Farage and Alex Salmond out of government.
ITV News Political Correspondent Emily Morgan on the Lib Dem's push for power.
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.