The European Commission chief, Jean-Claude Juncker, has said he feels “betrayed” by the “egotism” shown by Greece in failed debt talks.
He told a news conference that Greek proposals were “delayed” or “deliberately altered” and the Greek people “should be told the truth”, but the door was still open to talks.
Greece has called a surprise referendum and Greek banks are closed for a week.
European stock markets saw big falls on Monday after the weekend’s events.
The negotiations were not “a game of liar’s poker”, Mr Juncker said. “Either all win or all lose”.
He said the talks were broken “unilaterally” by the announcement from the Greek Prime Minister Alexis Tsipras that he was calling a referendum for 5 July.
The Greek government responded to Mr Juncker’s comments by saying: “An essential element in indicating good faith and reliability in negotiations is sincerity.”
Mr Juncker said that he still believed a Greek exit from the euro was not an option and insisted that the creditors’ latest proposal meant more social fairness.
German Chancellor Angela Merkel echoed those comments on Monday, saying Greece had received a “generous offer” but adding she would not be opposed to further talks with Greece after Sunday’s vote, Reuters reports.