Many Ukrainians advocate the "one nation - one language" principle, a fact that analysts say means the bill might backfire.
The language of Ukraine's former Soviet overlord dominates the city of 1 million - nearly half of them ethnic Russians - where a statue of Communist leader Vladimir Lenin still graces the main square two decades after the Soviet Union collapsed.
Famous for its coal mines, steel smelters and bloody gang wars of the 1990s, the home city of President Viktor Yanukovich has welcomed a move by his Regions party to restore Russian as the language for official business in Ukraine's east and south.
"Canada has two state languages, Switzerland has four, I think this is the right approach," said Volodymyr, a retired mining communications engineer who complained that translating technical documents into Ukrainian was a waste of time.
The language bill is widely seen as a bid by the party to revive ratings hit by public disgruntlement with economic hardship in time for a parliamentary election in October.
But whereas moves to promote regional languages elsewhere in Europe have caused little political pain,Ukraine's bill has touched such a raw nerve that it is now in limbo after fists flew in parliament and protesters clashed with police.
The fierce debate it has stirred over Russian influence was likely to cloud a visit by Russian President Vladimir Putin on Thursday to discuss the price Kyiv should pay for Russian gas.
It is also another complication for one of Yanukovich's top foreign policy goals, integration with Europe's mainstream.
The European Union is not even discussing membership yet and shelved an agreement offering closer ties after former prime minister Yulia Tymoshenko was jailed for abuse of power last October, a sentence seen byBrussels as an example of selective justice.
Many Russian speakers believe the new law protects against encroachment by "western nationalists" such as the introduction of mandatory Ukrainian dubbing of films by the government of previous president Viktor Yushchenko.
For its opponents it is a blow to the fragile sovereignty of a country long divided between regional powers and persecuted by Moscow's tsars and its Communist leaders. Some say it could end up splitting the country in two.
It triggered uproar in the western city of Lviv, a cultural opposite of Donetsk featuring medieval European architecture and a statue of Stepan Bandera, a World War Two nationalist leader who temporarily sided with the Nazi Germans against Soviet rule.
Historically a Polish city with a large ethnic Ukrainian population in adjacent rural areas, Lviv was annexed by the Soviet Union in 1939. Many of its residents - who almost all speak Ukrainian - equate Soviet rule with Russian occupation.
Opponents of the bill set up a tent camp in the city centre, blocked all entrances of the local government building and burned a Party of the Regions flag in protest.
"This bill aims to undermine the status of the state language," says Maria Zubrytska, a deputy rector at the Ivan Franko National University of Lviv.
"It is, above all, a threat to the authority of the constitution ... a new form of neo-colonialism."
HISTORY OF OPPRESSION
Ukrainian, an allied Slav language considered a mere dialect of Russian by the rulers of the Russian Empire - a view still held by some Russians - was barred from schools and printing presses in the 19th century.
The 1917 Bolshevik revolution brought only a temporary relief as new Soviet leaders soon began enforcing the use of Russian as a universal language across the USSR.
While the use of Ukrainian was not barred, Russian-language schools were more prestigious and offered better prospects for further education.
"As a first-grader, I once asked for a fairy-tale book in Ukrainian at the school library," says Natalia, an office worker in Kiev who grew up in the Soviet Union.
"The librarian refused, saying: 'You only start studying Ukrainian in the second grade'."
Soviet industrialisation campaigns of the 20s, 30s and post-war years brought an influx of millions of Russians who mostly settled in Ukraine's eastern regions rich with coal and iron ore deposits and were under no pressure to learn the local language.
The Crimean peninsula, given to Ukraine by Russia in 1954 by Soviet leader Nikita Khrushchev but the base for Russia's Black Sea fleet at Sevastopol, is another Russian-speaking stronghold.
According to a 2001 census, there were 8.3 million Russians in Ukraine but Prime Minister Mykola Azarov, an ethnic Russian himself who speaks Ukrainian only with difficulty, raised eyebrows last month when he said there were 20 million ethnic Russians in the nation of 46 million.
People in Donetsk, as well as other eastern and southern cities, already use Ukrainian quite rarely - mostly when dealing with government paperwork and going to cinemas.
Even court hearings, which by law must be held in Ukrainian, are often conducted in Russian and only translated into Ukrainian for records, locals say.
Donetsk bookseller Tetyana, 23, says books in Ukrainian occupy only 10 percent of her shelves at best. "There simply is not enough demand," she explains.
"The Ukrainian language just does not exist any more," chimes in her colleague from a nearby store who refuses to introduce herself. "All that is left is Surzhik (a Russian-Ukrainian pidgin)."
But many Ukrainians advocate the "one nation - one language" principle, a fact that analysts say means the bill might backfire. According to the Razumkov centre, a local pollster and think tank, the population is roughly evenly split on the issue.
In particular, 43.6 percent think that only Ukrainian should be state language, 25 percent support the idea of giving Russian official status in certain regions and 23.9 percent think it should be the second state language.
"Many people in the Party of the Regions are themselves questioning (the need for the language bill) because they understand that they have given their opponents a great way of mobilising (public support) against them," says Donetsk-based political analyst Volodymyr Kipen.
Iryna Chernichenko, a bilingual journalism teacher in Donetsk said it was a political game.
"I think a myth is being spread by certain politicians... about the oppression of the Russian language and it has been accepted as truth by some people," she said. "The adoption of this bill by parliament is splitting the country."
The bill is now in limbo after parliament speaker Volodymyr Lytvyn, a member of the ruling coalition, refused to sign it and threatened to resign. The chamber then went into recess until September.
Yanukovich, a Russian speaker who speaks Ukrainian at state and official functions and has back-pedalled on a 2009 pledge to upgrade Russian, has not said whether he will sign the bill into law if it lands on his table.
A think tank employed by his office, the National Institute of Strategic Research, advised against any language reforms over a year ago.
About a quarter of Ukrainians living in the eastern and southern regions believe the East-West schism over language and politics could eventually break up the country, it said.
"This picture demonstrates an extreme weakness, if not absence, of a common social and cultural foundation of the Ukrainian political nation and the presence of separatist and irredentist trends," it said.
"...Official recognition of non-state languages in certain regions will only complicate the situation and diminish the state's efforts at unification."