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.
More top news
Low-paid healthcare workers are having to pay the "extortionate" fees to park in front of their workplaces, a study shows.
After a cold start on Wednesday, it will be another day of sunshine and showers across many central and eastern parts.
It is claimed that both police and security services, including MI5, have been prevented from vast pools of data on the social media site.