- 4 updates
Deputy Prime Minister Nick Clegg said his plan to raise the income tax threshold above £10,500 before the next election was "certainly no secret" but it had not been "agreed yet" with David Cameron.
The Liberal Democrat leader told the BBC's Andrew Marr Show: "It's not agreed yet, it is something that I would like to see us deliver as a Coalition Government in the next budget.
"I've had to argue very strongly for each step of the increase in the allowance ... I've insisted all along that it is affordable because I think it's a fair thing to do".
However, Mr Clegg said the measure would not be seen in the Chancellor's upcoming Autumn Statement.
"Of course I need to persuade my Conservative Coalition partners - that's normal in a Coalition Government," he added.
Shadow treasury chief secretary Chris Leslie dismissed Nick Clegg's call for a raise in the income tax threshold, saying the coalition's changes had left working families worse off overall.
"Working people facing a cost-of-living crisis need help right now, but Nick Clegg's Government has instead prioritised a huge tax cut for those earning over £150,000," the Labour MP said.
"When it comes to people on middle and low incomes, the Government is giving with one hand but taking away much more with the other," he said.
"The Lib Dems need to explain how their proposal would be paid for and why they refuse to back Labour's plan to freeze energy bills and reform the market."
Nick Clegg is keen to claim political credit with another raise in the income tax threshold, a source close to the Lib Dem leader has said.
"Our polling shows that raising the tax allowance is both strongly associated with the Lib Dems and popular," the source said. "We know that we are on to a vote winner here."
Lib Dems said David Cameron argued in the televised debates before the last general election that raising the personal allowance to £10,000 would not be possible, though it has since occurred.
"The Tories once said this policy wasn't affordable but now they like to claim credit for it," the source said. "Will they now join the Lib Dems in going further and faster?"
The Liberal Democrats want the coalition to raise the income tax threshold above £10,500 by 2015, which could effectively mean a £100-a-year tax cut to 24 million basic rate payers.
The move, which would take half a million people out of income tax altogether, would represent a £1 billion tax giveaway before the next general election.
The Lib Dems have already seen the coalition achieve their manifesto commitment to raise the personal allowance to £10,000 - which was finally reached in the last Budget in March.
Lib Dem leader Nick Clegg will write to party activists next week calling for a "workers' bonus" to reward voters for the financial sacrifices they have made during the years of austerity.