* Lithuania aims to become 19th euro zone member in 2015
* ECB governing council votes would then start to rotate
* Smaller economies to vote less frequent than larger ones
* ECB executive board exempt from monthly vote rotation
* German politicians worry about reduced Buba influence
By Eva Taylor
FRANKFURT, Feb 4 (Reuters) - Lithuania's adoption of the euro next year will change the voting pattern at the European Central Bank, curbing smaller members' perceived influence and giving more weight to the centre.
Taking turns to vote will affect all euro zone members, but the damage will be more keenly felt in Germany whose once-mighty Bundesbank served as a blueprint for the ECB. It has since seen its influence weaken and support for its stern views on monetary policy diminish during the euro zone debt crisis.
Once national central bank governors, who gather twice a month at the ECB to discuss monetary policy, exceed 18 - their current number - they will be divided into groups of smaller and larger economies to ensure efficient decision making.
The five largest economies with the biggest financial sectors will share four votes. These are Germany, France, Italy, Spain and the Netherlands based on current rankings.
The remaining 14 countries will get 11 votes, but they will get to vote less frequently the more members join the governing council.
The system was set by the ECB and European Union leaders as far back as 2003. Only from next year though the numbers could get high enough to trigger the change.
The six members of the ECB's executive board, which implements monetary policy and runs the everyday business, are exempt from the monthly vote rotation and have permanent votes.
These seats have traditionally been occupied by the euro zone heavyweights Germany, France, Italy and until 2012 Spain. At the moment Portugal, Luxembourg and Belgium are also seated at the top table, but their presence is not set in stone.
MINNOWS SLIPPING THROUGH THE NET
Lithuania would fall into the group of the euro zone minnows with a population of around 3 million and a gross domestic product of about 33 billion euros, just over 1 percent of Germany's economy.
It is aiming to become the euro zone's 19th member next year, following its Baltic neighbours Estonia and Latvia, which joined in 2011 and 2014, respectively.
If all goes according to plan and Lithuania gets the green light this summer, Central Bank Governor Vitas Vasiliauskas will start travelling to Frankfurt on a regular basis from next year to help set the bloc's monetary policy.
It is difficult to say in what state the euro zone economy will be by then and it is unclear what the reduced influence of the smaller countries will mean for the ECB's monetary policy stance, but some of the side-effects are already clear.
"You won't be able to avoid a situation where the market gets very focused on the fact that one particular governor is not going to be voting at a particular juncture," said Nick Matthews, senior European economist at Nomura.
This could distract from the ECB's overall policy message.
Publishing the policy meeting's minutes - as it is being discussed at the moment - could be a way to showcase the nature of the debate and to give a voice to those who cannot vote. The council primarily tries to reach an agreement by consensus.
Deutsche Bank senior European economist Gilles Moec said the new pattern may also lead to more public statements from national central banks.
"If you are not voting, even if your vote wouldn't have changed anything, you probably want to reassert your influence by being bolder in your external communications," Moec said.
That would add to the cacophony of views, which sometimes confuses markets.
In Germany, the vote change will raise renewed criticism even though the Bundesbank will rank among the top-five and will therefore only have to sit out once every five months.
Conservative politicians have long called for a change of the "one member, one vote" principle to reflect that their country contributes just over a quarter of the ECB's capital.
In effect, Germany's Bundesbank has and will continue to have exactly the same vote as Malta or Cyprus, even though the latter two make up a fraction of the euro zone economy.
Norbert Barthle, a budget lawmaker in Chancellor Angela Merkel's Christian Democrats, is among those calling for a change of the rules, but such a step would require a change of European Union treaty for which a unanimous vote is needed.
"It is unimaginable that Germany as the ECB's largest shareholder should temporarily not have a voting right," Barthle told Reuters.
The Bundesbank itself takes a pragmatic view, stressing that all countries will continue to take part in the discussion and still have the right to speak. And after all, the governors are not representing their country's interests on the council.
Apart from that, the Bundesbank just installed its No. 2 on the ECB executive board. Sabine Lautenschlaeger started her eight-year term on Jan. 27, having served as the Bundesbank's vice president since June 2011.