London - Britain's ambassador to the United Nations, John Sawers, is to become the next chief of the country's overseas intelligence service (MI6) in November, the government announced Tuesday.

The 52-year-old top diplomat is to succeed John Scarlett, the publicity-shy spy chief whose reputation was badly dented by the service's role in drawing up the so-called Iraq dossier on the alleged existence of weapons of mass destruction under Saddam Hussein.

Sawers, who will oversee an espionage network that has switched its priorities from the post-war goal of fighting Soviet-style communism to watching al-Qaeda, worked as a key foreign policy adviser to former prime minister Tony Blair between 1999 and 2001.

In that role, he was deeply involved in the management of the Kosovo crisis and the Northern Ireland peace process. He has also held diplomatic posts in Baghdad and Washington, and was an ambassador to both Egypt and South Africa.

Scarlett is expected to be called as a key witness to an independent inquiry into the Iraq war announced by Prime Minister Gordon Brown this week.

The BBC said Sawers' appointment showed how much more open MI6 had become in recent years.

While Scarlett, who used to be known only as "C" to keep his identity secret, had played a key role in old-fashioned espionage, Sawers was a "highly recognizable" figure. (dpa)