The Liberal Democrats will pledge an extra £2.5bn for England’s education budget in their election manifesto.
The party said the cash would ensure spending was protected “from cradle to college” and went beyond other parties’ commitments on education.
Leader Nick Clegg will say the plans are all about boosting opportunity.
But the Conservatives said the Lib Dems offered “uncertainty for parents” while Labour said Nick Clegg’s party had “broken their promises” in government.
The BBC’s assistant political editor Norman Smith said he expected it to be a “minimalist, pared-back” document, with a focus on a few key priorities, after the party was unable to deliver the main commitment on tuition fees from 2010.
In other election news:
- UKIP is also launching its manifesto, with a pledge to employ 6,000 former army veterans in the police, prison service and Border Agency and spend 2% of national income on defence
- Labour is launching what it calls its women’s manifesto, with a pledge to allow working grandparents to share unpaid parental leave.
- The SDLP, which had three MPs in the last Parliament, is publishing its general election manifesto.
The Lib Dems have previously said they would protect the education budget, by ensuring spending rises in line with inflation.
Mr Clegg will now say that once the deficit has been eliminated in 2017-18, funding for two to 19-year-olds would increase in line with economic growth, which was 2.8% over the course of 2014.
Even with pupil numbers taken into account, the party said this increase would ensure the amount of money per child was protected over the course of the Parliament, amounting to an extra £2.5bn.
Analysis by Sean Coughlan, BBC education correspondent
The Liberal Democrats are trying to stake out a claim to be the party that makes education a spending priority, by the promise of an extra £2.5bn.
Their education-friendly image had taken some hard knocks from the tuition fee U-turn and being in a coalition government that frequently clashed with the teachers’ unions.
But they have put forward a spending plan which they hope will out-flank both the Conservatives and Labour.
Labour pledged to protect school budgets against inflation, while the Conservatives’ offer was to protect per-pupil spending at a time of rising pupil numbers.
The Liberal Democrats’ pitch is to combine both – promising to protect per-pupil spending in real terms , including for an extra 460,000 pupils.
But there is a tough warning from the Institute for Fiscal Studies that school costs are rising much faster than inflation and a looming school funding shortage will face whoever wins the election.
It said the cash was the equivalent of 70,000 teachers and 10,000 learning support assistants and amounted to £2.5bn more than Labour and £5bn more than the Conservatives would spend.
Pressure on education budgets is expected to increase in the next five years due to a sharp rise in enrolment in state schools, with the number of pupils under the age of 15 expected to go up by 9% by 2020.
The Conservatives have said they would protect the budget for 5-16 year-olds in cash terms, so that funding rises in line with pupil numbers but not in line with inflation or economic growth.
Labour, on the other hand, has said it would ensure the budget for 0-19 year-olds increased in line with inflation but not in line with increases in pupil numbers or economic output.
‘Cradle to college’
Education is the responsibility of the devolved administrations, and the Lib Dems said the funding implications for Scotland, Wales and Northern Ireland would be known after the next spending review.
Promising to protect the budget “from cradle to college”, Mr Clegg will say: “The manifesto has one simple ambition and word at its heart – opportunity.
“It’s a very old, liberal idea, the idea that everybody should be able to live out their life to the full regardless of the circumstances of their birth, regardless of the income of their parents, regardless of where they come from.”
- Balance the budget fairly through a mixture of cuts and taxes on higher earners
- Increase tax-free allowance to £12,500
- Guarantee education funding from nursery to 19 and qualified teachers in every class
- Invest £8bn in the NHS. Equal care for mental physical health
- Five new laws to protect nature and fight climate change
The manifesto is also expected to include pledges on balancing the books by 2017-18, raising the threshold at which people start paying tax to £12,500 and “parity of esteem” between mental and physical health services in the NHS.
Mr Clegg told the Guardian that he regarded the party’s main manifesto pledges “with a near religious status” and would fight for them irrespective of the outcome of the election.
No party would win an outright victory, he claimed, and, in that event, the Lib Dems would be a “rock of stability” in any prospective coalition.
“The looming question in the next phase of this campaign is whether there is to be a coalition of grievance, or of conscience,” he said.
A Conservative spokesman highlighted the drop in per-pupil funding during the first phase of the Lib Dem education plan, when the budget would be linked to inflation.
“The Conservatives are the only party who are prepared to protect the money that schools get for each pupil,” he added.
Labour said the Lib Dems had “broken their promises and backed the Tories all the way”.
UKIP’s pledges, also to be unveiled on Wednesday, include an in/out referendum on Britain’s membership of the European Union “as soon as possible”, a five-year ban on unskilled migrants coming in to the UK and £12bn for the NHS.
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