Prita Patel, Britain's overseas development secretary, resigned late on Wednesday after meeting Prime Minister Theresa May at 10 Downing Street.
May had ordered Patel to cut short an official visit to Africa and return to London following reports she had held unauthorized meetings with Israeli officials, XInhua reported.
Her resignation was the second major blow within days for May following the resignation of the defence secretary Sir Michael Fallon in the so-called "sex pest" scandal that has currently engulfed British politics.
The fate of May's deputy, First Secretary Damian Green, has yet to be decided with an ongoing investigation into allegations made against him which he denies.
May has also faced calls this week from the main opposition Labor Party to fire Foreign Secretary Boris Johnson over his handling of a case involving a British-Iranian national, jailed for allegedly spying in Iran.
Political commentators in London say the troubles surrounding May's front bench team could not have happened at a worst time. She heads a minority government with opinion divided in her own party over Britain's future relationship with the European Union.
Patel, seen as a rising star in Conservative politics and a future leader, caused anger at Westminster over a series of unauthorized meetings with officials of the Israeli government, including a meeting with Prime Minister Benjamin Netanyahu.
Before leaving on a three-day official visit to Uganda, Patel apologized to May and was reprimanded and reminded of protocols for such meetings with foreign officials.
During the last 24 hours, more information emerged about further unauthorized meetings Patel had been held, and her fate appeared to have been sealed.
It emerged that Patel had visited an Israeli military field hospital in the Golan Heights even though Britain has never recognized Israeli control of the area seized from Syria in the 1967 Six-Day War.