Former UK prime minister Tony Blair has resigned as Middle East peace envoy, an official has told the AP news agency.

He will quit the role - which he took up immediately after leaving Downing Street in 2007 - next month.

The Quartet was formed following the 1991 Madrid Conference, and is made up of representatives from the US, UN, EU and Russia.

It was created in an effort to mediate the Israel-Palestinian conflict.

Mr Blair was appointed as a Quartet envoy in 2007, following a request from the the administration of US president George W Bush.

But he was criticsed for his dual role as diplomat and businessman.

His clients included Abu Dhabi wealth fund Mubadala and PetroSaudi - an oil company linked to the ruling Saudi royal family.