A Government minister says Conservatives should apologise for breaking a manifesto commitment not to raise National Insurance contributions.
The comment by Mr Bebb, the Tory MP for Aberconwy, puts him at odds with the Treasury, which insists that the 2% hike in NICs for the self-employed does not amount to a breach of the election-time promise.
Mr Bebb, who is a Government whip as well as a minister in the Wales Office, told the Welsh-language BBC Radio Cymru: "I believe we should apologise. I will apologise to every voter in Wales that read the Conservative manifesto in the 2015 election."
The Conservative manifesto for the 2015 general election stated four times that the party "will not raise VAT, National Insurance contributions or Income Tax" over the course of the next five-year Parliament.
Chancellor Philip Hammond said his £2 billion increase in NICs did not breach the manifesto pledge because legislation introduced after the election to implement the so-called "tax lock" referred only to the Class 1 contributions paid by employees and not the Class 4 rate for the self-employed which was increased in the Budget.
However, the manifesto promise makes no distinction between different classes of NICs.
A Downing Street spokesman said that Theresa May continues to have full confidence in Mr Bebb.
Asked whether the Wales minister could face the sack over his comment, the spokesman said: "We have heard a number of opinions expressed today. The point is that this is a Budget about creating a better future for Britain while addressing an unfairness in the tax system."