The country’s President also accused the SPD politician of working for Vladimir Putin in an extraordinary late-night video address this evening. Mr Schroeder, 77, who served as Germany’s leader from 1998 to 2005, is close personal friend of Putin’s who met him last week.
He subsequently angered many with an interview given to Stern Weekly magazine and broadcaster in which he suggested Russia wanted a “negotiated solution”.
He added: “A first success is the grain deal, perhaps that can be slowly expanded to a ceasefire.”
Ukrainian presidential adviser Mykhailo Podolyak was swift to respond, dismissing Mr Schroeder as a “voice of the Russian royal court” and making it clear the grain agreement would not lead to negotiations.
Mr Zelensky went even further, saying: “It is simply disgusting when former leaders of major states with European values work for Russia, which is at war against these values.”
Ukrainian Foreign Minister Dmytro Kuleba said there was nothing more cynical than “Putin’s henchmen” saying Russia is ready for peace talks.
He tweeted: “We hear and see this ‘readiness’ every day: artillery strikes, missile terror against civilians, mass atrocity crimes.
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The grain agreement, brokered by the United Nations and Turkey, has been hailed as a rare diplomatic success in the more than five months of war since Putin sent his troops over the border on what he calls a “special military operation”.
But Mr Zelenskiy played down its importance, saying the shipment was a fraction of the crop Kyiv must sell to help salvage its shattered economy.
He explained: “The war is almost killing the economy. It’s in a coma. Russia’s blocking of the ports is a great loss for the economy.”
Speaking in March, former German MEP Hans-Olaf Henkel mocked Mr Schroeder for travelling to Moscow in an apparent attempt to broker a peace deal, less than three weeks after Putin ordered his full-scale invasion.
Mr Schroeder’s wife, Soyeon Schroeder-Kim, subsequently shared a picture on Instagram of herself praying, with the Kremlin in the background.
Mr Henkel told Express.co.uk: “Apparently, both Putin and Schroeder are somewhat in trouble.
“Putin’s Blitzkrieg didn‘t work as expected, Western unity proved much stronger than he ever thought and the sanctions bite much more than he anticipated.
“Schroeder has rightfully become a political pariah by supporting Putin‘s corrupt political regime and the absence of any criticism of Putin‘s aggressive war against a sovereign country and its civilians.”
Mr Henkel added: “Should Putin now realise that he went too far and needs a face saving way out, he could negotiate with Ukrainian President Zelensky directly. He wouldn’t need Schroeder.
“But also Schroeder needs an excuse for his long support of the Russian dictator.
“He has nothing to offer as a mediator and it is likely that by bestowing him with that role Putin does Schroeder a favour and not the other way around.”