The Liberal Democrats would raise capital gains tax for the wealthiest in order to pay for an increase in the personal allowance to £11,000 in the first year of a new parliament, Nick Clegg has revealed.

The deputy prime minister said his party wanted to get on with cutting income tax for workers straight away and would make sure the rise in the allowance happened by April 2016.

This is worth about £100 a year to workers who earn over next year’s income tax threshold of £10,500 per year - roughly 29 million people - although it does nothing for the lowest paid who are already exempt from paying the tax.

Clegg has already announced he has an ambition to raise the personal allowance to £12,500 a year – a policy matched by the Conservative party at its conference last week. After this point, he has said the party would prioritise taking more low earners out of paying National Insurance.

The Liberal Democrats have now gone a step further by promising a faster cut, which they said would be paid for by raising capital gains tax for higher earners.

The current CGT rate for the highest bracket is 28% and Lib Dem sources said they believed they could get a maximum tax revenue if the rate was about 35%, raising £500m a year.

Further measures include lowering the exemption threshold from £10,900 to about £2,500, raising around £250m a year. The party believes it can bring in a further £750m from cracking down on tax evasion.

In a dig at the Conservatives, who announced billions of pounds in unfunded tax cuts, Clegg said: “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.”

Although the Liberal Democrats are trailing in fourth place in the polls, it is possible the party could go into coalition either with Labour or the Conservatives again, depending on which is the largest party. This would put Clegg in a position to push for the policy in coalition negotiations.