BEIRUT- Shi'ite politician Nabih Berri, a close ally of the Iran-backed Hezbollah group, was re-elected for a sixth term as speaker of Lebanon's parliament in an uncontested vote on Wednesday.

Another Hezbollah ally, Elie Ferzli, was elected deputy speaker, reflecting a shift in Lebanon's political landscape in favour of the heavily armed Shi'ite Muslim group.

Berri then said President Michel Aoun would begin consultations with lawmakers on Thursday to pick Lebanon's next prime minister, likely to be the previous one, Saad al-Hariri.

Aoun is obliged to designate as prime minister the candidate with the broadest support among MPs.

Hezbollah, and groups and individuals that support its possession of arms, won at least 70 of parliament's 128 seats in the May 6 election. The result was a reversal of Lebanon's last general election in 2009, when anti-Hezbollah groups scored a majority.

Berri drew the votes of 98 of 128 MPs at the new parliament's first session. After being reappointed as speaker, a role he has held since 1992, he called for a new government to be formed as soon as possible.

Lebanon is under pressure to form a new government quickly to tackle a dire economic situation and unsustainable public debt levels.

Hariri, who headed the outgoing cabinet, faces tough negotiations to form a coalition government including all the main parties. He will lead a caretaker government until the new cabinet is agreed.

Berri, 80, heads the Amal Movement and has been allied with Hezbollah since the end of Lebanon's 1975-90 civil war.

Hariri, an opponent of Hezbollah, had declared support for the re-election of Berri as speaker.

Under Lebanon's sectarian power-sharing system, the speaker must be a Shi'ite Muslim, the deputy speaker a Greek Orthodox Christian, the prime minister a Sunni Muslim and the president a Maronite Christian.

Ferzli, like Berri and Hezbollah, has close ties to the Syrian government of President Bashar al-Assad. Hariri had declared his opposition to Ferzli's candidacy.

The deputy speaker position has been held by a Hezbollah opponent since 2005, the year Syrian troops were forced to withdraw from Lebanon after the assassination of Rafik al-Hariri, Saad's father.

(Reporting by Ellen Francis and Laila Bassam; Additional reporting by Dahlia Nehme and Lisa Barrington; Writing by Angus McDowall/Tom Perry Editing by Mark Heinrich) ((Ellen.Francis@thomsonreuters.com;))