The scripture reigns supreme in Shas decision-making

Shas has held cabinet posts in governments of both sides since 1992 - apart from a brief interruption in 2000 - and its spiritual leader commands a following of hundreds of thousands of the ultra-Orthodox faithful of Middle Eastern origin.

The party's insistence on the supremacy of the Jewish scriptures has posed serious questions about Israeli democracy.

Shas was established in the 1980s by an influential former Sephardic chief rabbi, Ovadia Yosef, who refused the graceful retirement expected of him after he failed to extend his term in the post.

The rabbi has, unilaterally, retained the title and picturesque costume of his former position ever since.

Party policy is set by its Council of Torah Sages, which the rabbi dominates. It is a world of apocalyptic religious discourse where decisions belong to God and those who interpret God's law.

Crumbling and corrupt: Shas' religious school system

From the sages, through the politicians, and down to the party's grassroots, Shas is also the master of sectarian politics, representing a minority which feels discriminated against in all spheres of life in Israel.

A crumbling network of religious schools are a mainstay of party activity, with 40,000 places to rear children in the Shas brand of Jewish fundamentalism.

Shas officials are renowned for bending and breaking the rules - including setting up fictitious religious institutions - to secure public funds to support their school system.

Future of Israel

The party has never been particularly hawkish on peace process issues, usually promoting a doctrine of withdrawal from occupied lands if that preserves Jewish lives.

Its position on Eretz or Greater Israel is therefore at odds with other ultra-Orthodox movements, which seek to secure Israeli sovereignty over all the lands they believe were promised to the Jews by God, whatever the cost.

Shas is the standard bearer for a constituency which wants more power than it was given in Israel's European-led, non-denominational Zionist past.

And in the past it has shown that it can paralyse or extend the life of an Israeli government.