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 called the Liberal Democrat manifesto "an insurance policy against a government lurching off to the extremes" after the election.
With neither Labour nor Conservatives making a breakthrough in opinion polls, Clegg said the big question for voters is which party will join David Cameron or Ed Miliband in coalition.
He urged voters to consider "what will become of Britain" if Ukip's Nigel Farage or the SNP's Alex Salmond get into government.
He pledged that Liberal Democrats would always act responsibly, fairly and "in the best interests of Britain" if they return to government as part of a coalition, promising, "We will add a heart to a Conservative government and we will add a brain to a Labour one."
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.