Under British protocol, a Cabinet minister would normally organise meetings through the foreign office and be accompanied by officials, and visits with Israelis would typically be balanced with meetings with Palestinians.
It is the second resignation in May's top team in a week, underlining her weakness at a time when she faces the complicated task of unravelling more than 40 years of ties with the European Union and holding a deeply divided party together.
Patel's meetings with Israeli officials, which May's office said they were not aware of, and a reported visit to an Israeli Army field hospital in the Golan Heights, have increased the pressure on the Prime Minister, who depends on a Northern Irish party in Parliament to pass legislation.
But while acting quickly to force Patel to resign, the loss of an enthusiastic Brexit campaigner from her cabinet team of top ministers could mean that May faces greater pressure from MPs to pursue a clean break from the EU.
"Priti is more popular than Theresa, and has more contacts and influence overseas," a senior Conservative source said.
Patel was sacked a week after May's ally Michael Fallon, her Defence Secretary, resigned in a sexual harassment scandal that has also caught up two other ministers, including her deputy, Damian Green.
Her Foreign Secretary, Boris Johnson, this week was pressed to apologise over remarks he made about a jailed aid worker in Iran, which critics said could prompt the Islamic Republic to hand her a longer jail term.
- Reuters, AAP
