We would make this change in the Autumn Statement of 2015, meaning that the tax cut would kick in in April 2016.
This is the first step on the way to raising the personal allowance to £12,500 - which will put £400 back in the pockets of 30m taxpayers, as well as taking a further one million people out of tax altogether.
Liberal Democrats will pay for the tax cut in 2016 by raising Capital Gains Tax for the wealthiest and cutting down on tax avoidance.
Once the party has raised the tax-free threshold to £12,500, we will then start to increase the National Insurance threshold, continuing to cut taxes for working people. Our long-term ambition is to raise this to the same level as income tax.
Nick Clegg said: "Liberal Democrats believe in opportunity for everyone, not just a few at the top, and letting you keep more of your own money is central to that. We have cut your taxes in this Parliament and we will continue doing just that in the next.
"It's easy to promise a tax cut, it's much more difficult, especially in the current economic situation, to say who pays. We are clear that we will pay for this tax cut for millions of working people by asking wealthier people to contribute more.
"This is about priorities. The Conservatives may have copied our flagship policy but they would pay for it in a deeply unfair way - by hitting the working poor.
"And the Conservatives want to cut taxes for the better off by nearly five times as much.
"The difference between the Liberal Democrats and the Conservatives is that we want to cut taxes for working people, paid for by the wealthiest, they want to cut taxes for the wealthiest, paid for by the working poor."