World Bulletin / News Desk
Patel held a 30-minute-long meeting with Prime Minister Theresa May at Downing Street, after being recalled from an official visit to Uganda.
In her resignation letter which she handed in after the meeting, Patel apologized for her actions.
"As you know from our discussions, I accept that in meeting with organisations and politicians during a private holiday in Israel, my actions fell below the high standards that are expected of a Secretary of State," she said.
"While my actions were meant with the best of intentions, my actions also fell below the standards of transparency and openness that I have promoted and advocated.
"I offer a fulsome apology to you and to the Government for what has happened and offer my resignation," she added.
Earlier this week, Patel was reprimanded over a series of 12 meetings with Israeli Prime Minister Benjamin Netanyahu and other officials in August, which was not discussed with the U.K. Foreign Office in advance.
In September, she had two more meetings with Israeli officials at which U.K. government representatives were not present.
Israeli Public Security Minister Gilad Erdan tweeted about a meeting he had with Patel in the British parliament on Sept. 7, describing it as "wonderful".
Patel then met an Israeli foreign office minister in New York on Sept. 18.
In a statement on Monday, Patel apologized for the August contacts and 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 underway.
"In hindsight, I can see how my enthusiasm to engage in this way could be mis-read, 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 apologize for it."
Local media this week reported comments from a Downing Street spokesman who said Patel had discussed the possibility of using British taxpayers' money to support a hospital run by the Israeli military in the Golan Heights for Syrian refugees.
Britain does not give financial aid to Israel's military.
At all but one of the meetings, Patel was accompanied by lobbyist Lord Polak, a leading member of Conservative Friends of Israel, The Guardian newspaper reported.
The revelations came in the same week that Foreign Secretary Boris Johnson faced stinging criticism of his remarks about a British-Iranian woman jailed in Iran.
Nazanin Zaghari-Ratcliffe was detained in Tehran last year and faced charges of trying to overthrow the Iranian government. She is now serving a five-year jail term but the sentence could be increased if she is convicted on additional charges.
Zaghari-Ratcliffe said she had been in Iran on holiday to visit relatives but last week Johnson said she had been teaching journalism. He was later forced to correct his remarks.