The Welsh Conservatives would cut the basic rate of income tax in Wales by 2p in the pound if they win the assembly election.
Powers to vary income tax will be devolved to Cardiff Bay under plans published by the UK government.
This is expected to happen within the next five-year assembly term.
The Tories previously suggested a 1p cut in the basic rate, and are offering a 5p cut in the higher 40% rate.
Writing in the Sunday Times, Welsh Conservative leader Andrew RT Davies said: “This election is a watershed moment for Wales, with the Assembly set to receive powers to vary income tax levels for the first time.
“At last we will have a mature, accountable legislature, and an executive which is forced to take responsibility for some of the money it spends and raises. A bona-fide Welsh parliament.”
The Conservatives would not raise any income tax levels, he added.
The basic rate of income tax is currently 20p, and the higher rate, levied on annual income above £43,000, is currently 40p.
Welsh Labour has already promised not to change income tax rates over the next five years.
Plaid Cymru say they would not increase income tax, but they would introduce a new “middle rate” of income tax, representing a small cut in the current higher rate.
The Welsh Liberal Democrats back a 1p cut in the basic rate, while UKIP wants a referendum to be held before the tax is devolved.
Chancellor George Osborne announced he was scrapping the requirement for a referendum on the issue while presenting his autumn statement in November.
All copyrights for this article are reserved to bbc uk