Britain's Prime Minister Theresa May leaves Number 10 Downing Street in London, Britain January 24, 2017. REUTERS/Stefan Wermuth

BELFAST (Reuters) - British Prime Minister Theresa May said on Friday that her chief enforcer in parliament had made an honest mistake by breaking a so called pairing agreement at a crucial vote and that he and the party’s chairman had apologized.

Julian Smith, known as the government’s chief whip, told some Conservative lawmakers to break a pairing arrangement with rival parties that ensures genuine absences do not skew votes in parliament.

Conservative Chairman Brandon Lewis followed the advice and voted with the government at a key Brexit vote on Tuesday even though his “pair”, Liberal Democrat lawmaker Jo Swinson, was away as she had just given birth.

When asked by a reporter if she could be trusted, May said: “There was an honest mistake made for which the chief whip and indeed Brandon Lewis have both apologized to the member concerned.”