As a diplomatic argument between London and Tehran grows, Britain's Foreign Office says non-essential embassy staff and their families can leave if they wish. But despite the deterioration in relations, Prime Minister Blair says he would like to continue dialogue with the Iranian leadership.
A Foreign Office spokeswoman says the decision to allow some staff to leave has come after an assessment of Wednesday's attack on the British embassy in Tehran.
In that incident, at least five shots were fired at the complex hitting some windows. No one was injured.
The embassy is closed until further notice.
Britain's Foreign Office in London characterizes the authorization to leave as strictly a security matter that should not be interpreted as a downgrading of diplomatic relations.
Diplomatic links have soured since the arrest two weeks ago of a former Iranian ambassador to Buenos Aires accused of complicity in the 1994 bombing of a Jewish community center that claimed 85 victims.
Hadi Soleimanpur has made two brief court appearances in London since his detention. Argentina is seeking his extradition from Britain.
While London maintains the possible extradition must be viewed in judicial terms, Tehran says it is politically motivated.
On Wednesday, Iran's Ambassador to Britain was recalled to Tehran for what are described as urgent consultations. It is not known if or when he will return to his post here.
Meanwhile, at his monthly news conference Prime Minister Tony Blair stressed that he wants to keep talking.
Mr. Blair urged Iran Thursday to meet its international obligations on its nuclear activities and to halt what he called support for terrorist groups.
Iran is under international pressure to sign an additional protocol to the nuclear Non-Proliferation Treaty to allow surprise inspections of its nuclear sites.
After a two-decade break in diplomatic relations, both countries resumed full contact at an ambassadorial level in 1999.