The Nord Stream 2 project is “political bribe money for loyalty to Russia,” Poroshenko told German business newspaper Handelsblatt.
Building it would mean “imposing an economic and energy blockade on Ukraine” he added, charging that the pipeline has “no economic justification”.
German Chancellor Angela Merkel has called Nord Stream 2 a purely “economic project” with no need for political intervention, but it has become an open wound in relations with eastern neighbours and the European Commission.
The pipeline would double the amount of Russian gas arriving in the European Union’s most powerful economy via the Baltic Sea – without transiting Ukraine – by late 2019.
Authorities in Germany issued the final permits needed for construction of Nord Stream 2 on its territory and in its waters to begin last month, although other nations’ green lights are still needed.
But “the Ukrainian transit pipeline is much cheaper and can be modernised cheaply and easily,” Poroshenko told Handelsblatt.
He accused Russia of being an “extremely unreliable partner” in energy provision, pointing to state-owned energy firm Gazprom’s refusal to pay Ukraine billions of euros after shutting off gas supplies in the middle of winter.
Gazprom accounts for around one-third of Europe’s gas supply.
Less and less has arrived via Ukraine in recent years. The reduction is part of Moscow’s conflict with Kiev which saw Russia annex the Crimean peninsula in 2014, prompting EU sanctions in response.
A rare cross-party alliance of high-ranking German politicians from Merkel’s Christian Democratic Union, the environmentalist Greens and pro-business Free Democrats warned in February against allowing Nord Stream 2 to go ahead.
It would “split the EU politically and call into question our solidarity with Poland, our Baltic neighbours, Slovakia, and Ukraine, but also Sweden and Denmark,” they wrote.
Also in February, Merkel clashed with Polish Prime Minister Mateusz Morawiecki at a Berlin press conference over the pipeline.
He warned that Russia must “not be allowed to have a monopoly and force its prices on the European Union”.
Ukraine has also urged sanctions against former German chancellor Gerhard Schröder over his vocal support of the Russian government and US$500,000-a-year (RM2.4 million) job on the board of Russian state-owned oil giant Rosneft, calling him “(Russian President Vladimir) Putin’s most important lobbyist”.