Chancellor Philip Hammond has said the government needs "flexibility" on taxes, hinting he is not fully committed to the Conservatives' former manifesto pledge not to increase income tax, national insurance or VAT.
The Conservatives have not yet finalised their manifesto, and are expected to do so within the next few days.
And, although Hammond has told the BBC he did not become a politician to "increase taxes", he has suffered defeat on tax before, when he was forced to make a U-turn over trying to increase tax on the self-employed in his Spring Budget.
Speaking to the BBC, Hammond said today: "We do need flexibility to manage the system and we do need to make sure that Theresa May and her government have a clear mandate to execute our plan.
"All chancellors would prefer to have more flexibility in how they manage the economy and how they manage the overall tax burden down [rather] than having to have their hands crossed."
The chancellor scrapped plans to raise national insurance contributions for the self-employed when he faced widespread criticism for breaking a manifesto promise not to increase taxes.
What our five year tax lock means for you. pic.twitter.com/fRT6Hp7BZX— David Cameron (@David_Cameron) April 29, 2015
The Treasury argued at the time that the manifesto pledge only applied to employed workers, but Hammond conceded that the Budget plan went against the "spirit" of the commitments made in 2015.