Poland and Hungary have temporarily halted imports of Ukrainian grain despite a warning from Brussels that such unilateral action would contravene EU trade policy.

After Moscow launched its full-scale invasion of Ukraine last year, the EU scrapped customs duties and quotas on Ukrainian grain imports and rerouted some shipments from blockaded Black Sea ports via Polish and Romanian roads and railway networks.

The announcement by Poland and Hungary is an attempt to placate their farmers amid a grain glut that has sent prices crashing in their domestic markets as cheap Ukrainian grain undercuts local producers.

Most of the grain was meant to be re-exported from the EU to the Middle East and Africa to help Ukraine’s economy and at the same time alleviate food shortages sparked by the war.

But the grain remained in countries close to Ukraine because of a shortage of trucks and trains to move it to neighbouring ports. A bumper grain harvest in central Europe meanwhile helped to avert a food crisis.

Struggling with high debt and weakening economies, poorer nations in Africa and elsewhere have also recently been seeking to curtail food imports.

Eastern European farmers have complained about the level of compensation offered by Brussels.

The European Commission on Sunday said it was aware of the move by Warsaw and Budapest regarding the import of Ukrainian grain and other agricultural products. Miriam Garcia Ferrer, commission spokesperson for trade and agriculture, said: “Trade policy is of EU exclusive competence and, therefore, unilateral actions are not acceptable. In such challenging times, it is crucial to co-ordinate and align all decisions within the EU.”

Opposition parties in Poland have seized on the grain dispute to attack the conservative government, which is relying on the backing of voters in farming regions to win parliamentary elections scheduled for this autumn.

The issue this month forced the resignation of the country’s agriculture minister, Henryk Kowalczyk, who quit while blaming Brussels for not providing sufficient help for Polish farmers.

Poland’s decision to temporarily halt some Ukrainian imports was announced by Jarosław Kaczyński, the leader of the ruling Law and Justice party, during a party convention in Łyse on Saturday.

Hungarian agriculture minister István Nagy said in a separate statement that the temporary ban on imports of grain and oilseeds from Ukraine, as well as several other agricultural products into Hungary would be in place until June 30.

Nagy said that the timeframe should be enough for the EU to come up with appropriate rules, including a review of the free trade regime with Ukraine. He added that Hungary and Poland were acting “in the absence of meaningful EU measures”. Poland’s new agriculture minister Robert Telus also indicated last week that his country wanted an import ban until at least the start of July.

The EU moratorium on tariffs ends on June 30 but the commission has proposed extending it for another year. Member states, including Spain and the Netherlands, want Ukrainian cereals for animal feed.

During a visit to Warsaw on April 5, Ukrainian president Volodymyr Zelenskyy had pledged to resolve a dispute that had become one of the few areas of discord between Kyiv and Warsaw, from where the Polish government has spearheaded western efforts to send more weapons to Ukraine.

On Saturday Ukraine’s agriculture minister, Mykola Solski, said Kyiv understood the difficulties facing farmers in Poland but insisted “it is the Ukrainian farmer who is in the most difficult situation. We ask the Polish side to take this into account.”

According to the Polish ban regulation published at the weekend, Warsaw will stop imports of several other farm products from Ukraine, ranging from beef and pork to eggs and dairy products. The ban also covers Ukrainian produce specifically earmarked for transit through Poland.

For several weeks farmers in Poland, Romania and other countries on the eastern flank of the EU have been holding protests and blockading roads to demand more compensation and to halt the arrival of Ukrainian grain.

Last month the commission proposed that affected EU farmers receive a total of €56.3mn to mitigate the fallout caused by an “excessive supply” of Ukrainian grain imports. It is considering extending aid to more countries soon, a move that must be approved by member states.

The decision was taken after Romania, Bulgaria, the Czech Republic, Hungary, Poland and Slovakia wrote to Brussels to demand urgent measures. Slovakia is also holding national elections in September.