A UN human rights panel has said that Latvia's language rules are discriminatory because they limit jobs for Russian-speaking and other minorities.
The UN Human Rights Committee's scrutiny of Latvia comes as the Ukraine crisis has made Russian-speakers' rights a headline issue in former Soviet-ruled nations, after the Kremlin claimed abuses forced it to intervene in Crimea.
In a report after a hearing with Latvian officials earlier this month, the committee spotlighted the status of "non-citizens" and linguistic minorities in the Baltic state.
Since Latvia's independence from the crumbling Soviet Union in 1991, the Kremlin has regularly condemned it over the lot of Russian-speakers, earning Latvian accusations of meddling in its affairs.
Latvian is the only official language in the country of two million people, where around a quarter of the population are Russian-speakers.
The committee said it was concerned over the "discriminatory effects of the language proficiency requirement on the employment and work of minority groups and at the exclusion of 'non-citizen' residents from certain professions in the private sector".
Latvia argues that its legislation was essential to right the wrongs of the Soviet era.
Moscow annexed Latvia during World War II. Thousands of Latvians were deported to Siberia, and huge numbers of Russian-speakers sent in over the ensuing decades.
After 1991, Latvia did not grant automatic citizenship to Soviet-era arrivals and their offspring, bringing in language tests and creating a special resident status for those who did not apply or failed.
The country's pre-Soviet Russian and ethnic Polish minorities were given citizenship, however, because their ancestors had held it before the war.
The number of non-citizens has declined due to naturalisation, but remains around 13 percent of the population of Latvia, which joined the European Union and NATO in 2004.
In 2012, Latvia's voters rejected efforts by Russian-speaking campaigners to give their language equal status via referendum.
Later that year, the authorities refused a plebiscite on granting automatic citizenship.
The UN committee urged Latvia to "enhance its efforts to ensure the full enjoyment" of human rights as set down in an international treaty and to facilitate integration.
It called for a review of the language law "to ensure that any restriction on the rights of non-Latvian speakers is reasonable, proportionate and non-discriminatory" and make it easier for them to deal with the authorities.
Latvia should also consider widening the number of people eligible for free-language lessons, and stop budget cuts for minority-language education, it said.