FACTBOX: New rules for Russia's parliamentary election

(Reuters) - Russia was voting on Sunday in a parliamentary election expected to hand a big victory to President Vladimir Putin's United Russia party and help him keep a hold on power after his term ends next year.

Since the last election to the 450-seat lower house of parliament, or State Duma, electoral rules have undergone major changes.

Kremlin critics say these changes benefit United Russia while disadvantaging smaller opposition parties. Supporters of the changes say they streamline the electoral system and are in line with practices in developed democracies.

Here are the main changes:

-- In previous elections, half the lawmakers were chosen on a party list system and half directly from constituencies. The constituencies have now been scrapped. Lawmakers can only win election based on nationwide support for their party list.

-- The threshold for parties to qualify for seats in the Duma has been raised from 5 percent of the vote at the last election in 2003 to seven percent now.

-- Voters can no longer tick the "against all" option on the ballot paper. Opposition parties said this option provided an opportunity for voters to register their protest against the political system.

-- The minimum turnout threshold of 25 percent for the election to be valid has also been dropped. There is now no minimum turnout requirement.

-- The process for registering a political party -- without which a party cannot apply to compete in an election -- was amended. Some in the opposition say the new procedures are so burdensome that, in effect, they exclude smaller parties with limited resources from the political process.

-- Restrictions on what can be said during a campaign were tightened. "Negative information" about other parties cannot be broadcast on television. New legislation has also widened the definition of extremist pronouncements and toughened punishments for anyone convicted of making them. The new law has been used to start a prosecution against a leading member of the Yabloko opposition party over his criticism of the Kremlin.

-- Parties cannot form blocs to contest the election.

-- Lawmakers cannot switch parties after they have been elected.

-- Parties already represented in parliament qualify automatically for the election. Those that are not can either submit a list of 200,000 signatures, or a cash deposit. The size of the deposit has increased from 37.5 million roubles ($1.55 million) in 2003 to 60 million roubles at this election.

-- Parties must also have at least 50,000 members, up from 10,000 in 2003, and establish branches with at least 500 members in half of Russia's regions.

-- State funding for registered parties has increased since 2003. Donations to parties cannot be made anonymously or by foreign countries, companies or citizens and tight controls have been introduced on spending and maximum donations.

(Reporting by Conor Sweeney; Editing by Charles Dick)