* Legislation would let regions allow Putin to choose candidates
* Bill wins preliminary approval in State Duma
* Popular elections were reinstated last year
By Maria Tsvetkova
MOSCOW, Jan 24 (Reuters) - Russia's parliament has given preliminary backing to a bill that would enable the country's 83 regions to scrap popular elections of their leaders in favour of a system that would let President Vladimir Putin choose candidates instead.
Opponents said the bill, approved in a 403-10 vote late on Wednesday after the first of three readings in the lower house would be a step backwards for democracy in Putin's new term. The lower house is dominated by Putin's United Russia party.
Putin scrapped popular elections of regional governors as part of a drive to tighten his grip on the political system in his initial 2000-2008 presidency.
The elections were reintroduced last year amid a wave of opposition protests that drew tens of thousands of Russians tired of Putin's dominance and eager for a stronger political voice.
Critics of Putin say the rules favour United Russia as it is, and its candidates won all five governorships at stake in elections last October.
The proposed law would allow each region to abandon direct elections and put in place a system under which Putin would name three candidates and the regional legislature would elect one of them as governor.
Backers of the bill suggest it is mainly intended as a means to scrap popular elections in regions with ethnically mixed populations, such as the mostly Muslim provinces of the insurgency-plagued North Caucasus.
The Kremlin is concerned that votes in those regions could involve candidates whose loyalty is in question or spark unrest.
The financial daily Vedomosti reported on Thursday that Putin wants to use the legislation to choose the leaders of the North Caucasus provinces of Dagestan and Ingushetia, bordering war-scarred Chechnya, this autumn. The Kremlin declined immediate comment.
Critics of the president suspect the law will be used in any region where United Russia, which is far less popular than Putin himself and saw its Duma majority sharply reduced in the December 2011 parliamentary election, fears it could face a strong challenge.
Dmitry Gudkov, an opposition lawmaker and a leader of the protests against alleged fraud on behalf of United Russia in that election, called the proposed law undemocratic and discriminatory.
"What has happened to make you think that citizens of certain regions do not deserve direct elections of their governors, and why are you also trying to guarantee that United Russia candidates will take power in regions where its level of support has fallen?" he said during the Duma debate.
Putin has said he is improving democracy in his new six-year term, which began last May, citing plans for a system under which half the Duma's 450 deputies would be elected directly, instead of from party lists. Critics say the initiative will favour United Russia because it holds the levers of power nationwide. (Reporting by Maria Tsvetkova; Writing by Steve Gutterman; Editing by David Brunnstrom)