Worldwide development secretary Priti Patel has admitted foreign secretary Boris Johnson did not know about her trip to Israel until she was there - and revealed a slew of meetings not previously disclosed.
Shadow Cabinet Office minister Jon Trickett said Ms Patel should face a probe led by the standards advisor, after she was reprimanded personally by the PM.
She said they had also been attended by Stuart Polak, the honorary president of the Conservative Friends of Israel and an influential pro-Israel lobbyist.
Patil said she had met with prominent Israeli figures, including Prime Minister Benjamin Netanyahu, the director general of the Israeli Foreign Ministry, Yuval Rotem, and opposition leader Yair Lapid. United Kingdom ministers are required to notify the Foreign Office when conducting official business overseas, but Patel admitted that she failed to do so.
Patel blamed her "enthusiasm to engage" for her failure to tell the Prime Minister and Foreign Secretary Boris Johnson about her high-level encounters, the Daily Mail adds.
Priti Patel is facing fresh calls to resign after failing to turn up to answer questions from MPs about her secret Israel meetings.
A Number 10 spokesperson said Mrs May had "full confidence" in her International Development Secretary and that she had not broken the ministerial code.
DOWNING Street demanded Priti Patel come clean about any more secret meetings with foreign politicians, as her Cabinet career hung by a thread. The Foreign Office was aware of the visit while it was underway, but were not informed about it in advance. The secretary of state would like to take this opportunity to clarify that this was not the case.
The minister said the Department for International Development (Dfid), Patel's own department, was made aware of the meetings by the Foreign Office on the same day. "I regret it and apologize for it".
The only assurance the Development Secretary was able to give No10 was that she hadn't "organised meetings with foreign Governments outside of the normal channels while on holiday".
The Netanyahu meeting included "prospects for closer collaboration between Israel and the United Kingdom on development and humanitarian issues", Israel-based newspaper Haaretz reports, noting that no minutes were kept.
On Tuesday No.10 confirmed Patel had suggested the United Kingdom send aid money to the Israeli army in the Golan Heights.
"The prime minister met the secretary of state this morning to remind her of the obligations which exist under the ministerial code".
"The Prime Minister welcomes the Secretary of State's clarification about her trip to Israel and has accepted her apology for her handling of the matter", the spokesman said.