The Israelis used “Trojan horse” spy software to record her messages, including e-mail exchanges with her husband, and forward them to a server computer.

Intelligence sources quoted in an Israeli newspaper admitted to the operation after police arrested 22 suspects in Israel’s biggest industrial espionage scandal last week.

The so-called Trojan Horse affair involved leading defence contractors stealing secrets from rivals by sending spy software to their computers disguised as a package of confidential documents. The programme recorded every keystroke and collected business documents and e-mails, which it then sent to a server computer registered in London.

Intelligence sources claimed the Syrian leader and his wife had proved ideal targets. Assad is said to be addicted to computer games.

Asma, his wife, is a computer science graduate from King’s College London, and is known to spend long hours corresponding online with her friends and family.

The sources claimed Assad was aware that Israeli intelligence experts had gained access to all his wife’s e-mails and documents and had complained about it to “some European leaders”.

Another military intelligence expert said: “The wives of leaders are soft targets.”

Most leaders, including Assad, would have well- protected computers, he said, but those belonging to their spouses were less secure. “Sometimes they do not even have a basic firewall.”

Syria’s first lady, the former Asma al-Akhras, now 29, graduated in 1996 and worked as an economist for Deutsche Bank and JP Morgan. She married Assad, who trained as an eye surgeon in London, in December 2000.

The intelligence official said Asma’s personal correspondence was of little value but the bugging provided an ideal method of monitoring the thoughts of the president.

“Israel is, of course, interested in the husband, not the wife,” he said. “Assad, even after five years in power, is an enigma.”