Cabinet minister Priti Patel has apologised for failing to give neither Theresa May or Boris Johnson the heads-up about meeting Israel's prime minister.
The International Development Secretary spent 12 days in the country August on a family holiday in August, but also spent her time meeting top ministers, officials, businesses and charities.
When conducting official Government work overseas, ministers are supposed to tell the Foreign Office.
But Ms Patel has now admitted she gave no advance notice of her trip.
Downing Street has also revealed the Prime Minister was in the dark over Ms Patel's meeting with Israeli leader Benjamin Netanyahu for more than two months, until last Friday.
Ms Patel's actions have prompted calls for an investigation, with the senior Tory accused of breaching ministerial rules and misleading the British public.
On her return from the trip, Ms Patel ordered new work in her department on UK-Israeli partnerships.
Ms Patel was ordered to Number 10 on Monday, with Mrs May reminding her "of the obligations which exist under the ministerial code".
But the Prime Minister's official spokesman insisted Ms Patel had given "full details in an open and transparent way of everyone she'd met with" when the nature of her trip was first reported on Friday.
"The important point here is that no UK interests were damaged or affected by the meetings which took place and the secretary of state has apologised for the way she handled this matter," the spokesman added.
"The code is not explicit in this area and one of the things which will follow from this is that the Prime Minister has asked the Cabinet Secretary to look at how the code can be made clearer in this respect."
On Monday, Ms Patel was forced to clarify remarks she previously gave to the Guardian newspaper about the trip.
Her department admitted these may have formed the impression she had given Mr Johnson prior notice of her visit, and that those publically reported meetings were the only ones to have taken place.
Ms Patel also offered an apology and published a full list of her meetings, which were arranged by Tory peer Lord Polak, the honorary president of Conservative Friends of Israel.
She said: "This summer I travelled to Israel, on a family holiday paid for myself.
"While away I had the opportunity to meet a number of people and organisations. I am publishing a list of who I met.
"The Foreign and Commonwealth Office was aware of my visit while it was under way.
"In hindsight, I can see how my enthusiasm to engage in this way could be misread, and how meetings were set up and reported in a way which did not accord with the usual procedures.
"I am sorry for this and I apologise for it."
Shadow international development secretary Kate Osamor suggested Ms Patel should quit over the row.
The Labour MP posted on Twitter: "Priti Patel breached Ministerial Code, and now caught misleading British public.
"If she doesn't resign, May must launch investigation."