The letter criticises KAN's alleged complicity in Israel's actions against Palestinians and cites the broadcaster's controversial coverage of the 2024 contest.
The former contestants accuse the EBU of hypocrisy for allowing Israel to participate while previously banning Russia, and demand an end to what they call a double standard.
This year's Eurovision contest, held in Basel, Switzerland, will feature Israeli contestant Yuval Raphael, a survivor of the October 7 attacks by Hamas.
Several broadcasters and organisations have previously protested Israel's participation in Eurovision, citing the ongoing conflict.