About 75% vote against constitutional recognition for mother tongue of about a third of the population

Latvian voters have resoundingly rejected a proposal to give official status to Russian, the mother tongue of their former Soviet occupiers and a large chunk of the population.

Russian is the first language for about a third of the Baltic country's 2.1 million people, and many of them would like it to be a national language to reverse what they claim has been 20 years of discrimination.

But for ethnic Latvians the referendum was an attempt to encroach on Latvia's independence, which was restored two decades ago after half a century of occupation by the Soviet Union since the second world war.

Many Latvians still consider Russian, the lingua franca of the Soviet Union, as the language of the former occupiers. They also harbour deep mistrust towards Russia and worry that Moscow attempts to wield influence in Latvia through the ethnic Russian minority.

"Latvia is the only place throughout the world where Latvian is spoken, so we have to protect it," said Martins Dzerve, 37, in Riga, Latvia's capital. "But Russian is everywhere."

With more than 93% of ballots counted, 75% of those who turned out to vote said they were against Russian as a national language, according to the national election commission.

But in the eastern region of Latgale, which straddles the border with Russia, a majority of voters approved changing the constitution to make Russian a national language. The region is Latvia's poorest and has a high percentage of ethnic Russians and other minorities.

"Society is divided into two classes – one half has full rights and the other half's rights are violated," said Aleksejs Yevdokimovs, 36. "The Latvian half always employs a presumption of guilt toward the Russian half, so that we have to prove things that shouldn't need to be proven."

More than 70% of registered voters cast ballots, considerably more than in previous elections and referendums. Long lines were seen at many precincts both in Latvia and abroad, with voters in London reportedly braving a three-hour wait.

In Chicago, Mara Varpa, 57, said she voted against the proposal since Latvian was an integral part of the national identity and should therefore remain the sole official language. "I don't think there should have been a referendum to begin with because it's already in the constitution, but since there was I had to vote," Varpa said.

Though the Russians who spearheaded the referendum admitted they had no chance at winning, they at least hoped the approximate 25% support would force Latvia's centre-right government to begin a dialogue with minorities.

Hundreds of thousands of Russians, Belarussians and Ukrainians moved to Latvia and the neighbouring Baltic republics during the population transfers of the Soviet regime. Many of them never learned Latvian and were denied citizenship when Latvia regained independence, meaning they do not have the right to vote or work in government.

According to the current law anyone who moved to Latvia during the Soviet occupation, or was born to parents who moved there, is considered a non-citizen and must pass the Latvian language exam in order to be naturalised.

There are approximately 300,000 non-citizens in Latvia.

Politicians and analysts said the plebiscite would widen the schism in society and the government would have to undertake serious efforts to consolidate the two main language groups. Many believe the minority will keep up the pressure, calling for more referendums to change Latvia's constitution for minorities' benefit.

• This article was amended on 20 February 2012 to make clear that 75% of those who turned out to vote said they were against Russian as a national language, rather than 75% of those registered to vote.