Greste was one of four Al-Jazeera journalists from the Cairo news team arrested on terrorism charges in December. A cameraman was released. Producers Mohamed Fahmy and Baher Mohamed remain in custody.
Two additional Al-Jazeera journalists, Abdullah Al Shami and Mohamed Bader, have been detained in Egypt since September.
At a news conference in London on Wednesday, Al-Jazeera English manager Heather Allan said of the Cairo team "We were doing nothing more than our jobs there that any one of our colleagues would be doing in Egypt at the moment."
The Egyptian police accused Al Jazeera English in Cairo of being a mouthpiece for the Muslim Brotherhood and using their broadcast location at the Marriott hotel as a meeting venue for Muslim Brotherhood members, an organization the Egyptian government deemed a terrorist group last month.
Following the the arrest of Greste and his colleagues in December, prosecutor Ahmad El-Rakib released a statement saying Al-Jazeera's Cairo news team members were charged with "joining a terrorist organisation, publishing false news harming national security, terrorising people and harming the people’s general benefit, and possessing broadcast equipment without licence."
An Al-Jazeera spokesman stated "We will continue to pursue all avenues to get our journalists back, and are grateful for all the support we have received. It is clear this is not just Al Jazeera’s campaign, but one taken on by all freedom-loving people around the world.”