Poland is marking the 90th anniversary of its independence, but anti-communist icon Lech Walesa has not been invited to attend the official festivities.
President Lech Kaczynski has not invited the 1980s Solidarity leader and former president to a Warsaw gala ball, due to be attended by some 800 guests.
Mr Kaczynski said he had been insulted by Mr Walesa so often that he did not want subject himself to more.
Mr Kaczynski's slight has angered government and church officials.
Lech Walesa is an icon in his homeland for his role in toppling communism in 1989, the BBC's Adam Easton in Warsaw says.
The former shipyard worker went on to become president in 1990-95. He was also awarded the Nobel Peace Prize in 1983.
"Every citizen - including you and me - has the right not to be insulted with extremely boorish words," President Kaczynski told Poland's TVN24 television on Monday, referring to his decision to snub Mr Walesa.
The two leaders fell out during Mr Walesa's presidency.
Mr Kaczynski had worked as Mr Walesa's adviser but was sacked in 1992. Their relationship has deteriorated since then.
Mr Kaczynski has even accused Mr Walesa of being a communist secret police informer in the 1970s - an allegation the former president vehemently denies.
Mr Walesa himself has made light of the latest snub, saying: "It's too bad I wasn't invited because I really wanted to party and dance with Mrs Kaczynska" - a reference to the president's wife.
But Mr Kaczynski is now facing growing criticism for the slight.
Polish Prime Minister Donald Tusk has said he is not planning to attend Tuesday' gala at Warsaw's Opera House, and is sending Foreign Minister Radek Sikorski as the government's representative.
However, Mr Sikorski has admitted that he will be lost for words if any of the world leaders asks him why Mr Walesa is not at the event.
"What do I tell our foreign guests if they ask me: 'Why didn't you invite the best-known Pole in the world, who we believe helped overthrow communism and contributed to freeing Poland and the world from totalitarianism?'" Mr Sikorski said earlier this week.
The archbishop of Gdansk, the birthplace of Solidarity, has said that Mr Walesa should top the guest list.
"Thanks to Walesa, a sovereign Poland joined a free world and a united Europe - it is precisely Walesa who had the dominant role in all of this," Archbishop Tadeusz Goclowski said.