Priti Patel, minister for international development, had issued a formal apology yesterday for holding undisclosed meetings during a holiday visit to Israel.
Downing Street said the premier had accepted her apology and considered the matter closed.
However, it emerged today that May has called for a review of the ministerial code of conduct to prevent a similar situation arising in future.
Ministers are required to tell the UK Foreign Office when they are conducting official business overseas, but a BBC report had claimed last week that British diplomats in Israel were not informedabout Patel's meetings which included a meeting with Israeli Prime Minister Benjamin Netanyahu and other political figures as well as charity organisations.
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Opposition parties had called for Patel, the senior-most Indian-origin member of May's Cabinet, to resign as minister in charge of the Department for International Development (DfID) and the country's aid budget if it emerges that she breached the ministerial code of conduct.
Downing Street has also been forced to deny that her meetings in the country had led to any change of political stance on the region.
"There hasn't been any change in policy resulting from that. There is no UK financial support for the Israeli army," a Downing Street spokesperson said after it emerged that in the wake of her visit in August, Patel had discussed potentially providing some of Britain's aid money to Israel's armed forces which run field hospitals in the Golan Heights area.
The issue of undisclosed meetings also found its way to the House of Commons today in the form of an urgent question from the opposition, where Patel's minister of state for the Middle East, Alastair Burt, defended his boss' actions as she is on a visit to Africa this week.
"The meetings were not particularly secret...If I had gone to Israel, I would have wanted a schedule like this," he told MPs.
The issue has only added to May's woes amid the sexual misconduct scandal that has engulfed UK parliamentarians which has already lost her a key Cabinet ally, Michael Fallon, who stepped down as defence minister last week.