Vladimir Putin is "weaponising Ukraine's crops" as "a blackmail tool" for the rest of the world, Poland's prime minister said at the World Economic Forum in Davos.
Mateusz Morawiecki told the BBC it was like what "Stalin did in 1933".
In a wide-ranging interview, he also warned that "only Putin" would be "happy" with a UK-EU trade war over the Brexit deal for Northern Ireland.
Ukraine's inability to export its grain has led to global food prices soaring.
It has also raised the prospect of famines in the countries which depend on its exports.
Mr Morawiecki said that this was "part of [Mr Putin's] strategy" in order to "create ripple effects in Northern Africa and huge migration waves".
His warning was echoed by the European Commission President, Ursula von der Leyen, who told delegates in Davos that Russia was using "hunger and grain to wield power".
"Global co-operation is the antidote to Russia's blackmail," she said.
Fears are rising that the Black Sea blockade is causing a global food crisis.
On Monday, Ukraine's deputy Prime Minister urged the international community to create a "safe passage" to enable the millions of tons of grain stuck in Ukraine to leave the country.
Yuliia Svyrydenko, First Deputy Prime Minister of Ukraine, told the BBC that some sort of "corridor" was needed.
A UK government spokesperson said the country was working "intensively" with partners to find ways to allow grain exports to resume.
However, there are "no current plans" for Royal Navy warships to help break Russia's blockade, the spokesperson added.
