During a speech today, he said Britons should be allowed to keep hold of what they earn, and that they have paid “enough tax”.
"It's time for waste in government to go. It's time for reform of welfare. It's not time for higher taxes on working people," he said.
The Conservatives have already said in their manifesto that they will not increase income tax, national insurance or VAT, but the new promise would take it further by making any hikes illegal. Cameron said the law would be passed within 100 days of a Conservative success on 7 May.
The other parties have been very critical of the pledge, with the Liberal Democrats describing it as a “gimmick”.
"This is yet another gimmick from David Cameron to deflect attention from the fact that the Tories have abandoned the plan followed by the coalition and instead want to slash and burn support for millions of families," a party spokesman told Reuters.
Labour, meanwhile, argued that the sums wouldn't add up, and the law would only work by cutting tax credits for low earners.