(Bloomberg) -- Just when it seemed she’d made it to the safety of a long summer vacation, U.K. Prime Minister Theresa May was thrown into a fresh storm -- this time over the allegedly underhand tactics her most senior political enforcer used to win a crucial vote in Parliament.

Government Chief Whip Julian Smith is said to have told some Tory lawmakers to break an agreement with rival parties under which members of Parliament are excused if they are too ill to vote, or are unavoidably absent, according to the BBC.

Now Conservatives are growing increasingly angry at the breakdown in “tradition and trust” and are suggesting that Smith may have to resign if it’s true that he ordered lawmakers to break the convention. “If true this is appalling and those responsible must resign. If we cannot behave with honor we are nothing,” Anna Soubry, a Tory MP, tweeted on Thursday.

Read more: U.K.’s May Pays Price of Trust to Survive in Tory Brexit War

Peter Bone, a pro-Brexit Tory, said he was “very concerned” to hear that the convention was broken. Opposition MP Jo Swinson, who is away on maternity leave, was meant to be “paired” with Tory party chairman Brandon Lewis, which would have meant he didn’t vote in order that she wouldn’t need to.

But during Tuesday’s intense battle to get May’s customs bill through the House of Commons, Lewis did vote -- and helped to ensure the government won. Both Lewis and Smith have apologized for the “mistake,” while May herself has said it was not acceptable.

Speaking on condition of anonymity -- because government officials conventionally share responsibility -- one minister told Bloomberg: “There must be honor and trust in pairing.” Another agreed he had to go.

Another senior Conservative stopped short of calling for the chief whip to quit but said there is a growing realization that Smith has broken one of the most important unwritten rules of whipping.

The Conservative Party headquarters was not immediately able to comment.

(Updates with second minister.)

--With assistance from Christopher Kingdon.

To contact the reporters on this story: Tim Ross in London at tross54@bloomberg.net;Alex Morales in London at amorales2@bloomberg.net;Kitty Donaldson in London at kdonaldson1@bloomberg.net

To contact the editors responsible for this story: Flavia Krause-Jackson at fjackson@bloomberg.net, Emma Ross-Thomas

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