Spanish Prime Minister Pedro Sanchez. AFP
The intervention by Sanchez, one of the most outspoken critics of Israel's devastating war in Gaza, comes after protests against Israeli participation marked last weekend's extravaganza in Switzerland.
Russia has not been allowed to participate in Eurovision since its 2022 invasion of Ukraine.
"Therefore Israel shouldn't either, because what we cannot allow is double standards in culture," Sanchez said at an event in Madrid.
"Spain's commitment to international law and human rights must be constant and must be coherent. Europe's should be too," added the Socialist leader.
Ahead of the Eurovision final on Saturday, Spanish public broadcaster RTVE aired a message in support of Palestinians -- despite being warned to avoid references to Gaza by Eurovision organisers the European Broadcasting Union (EBU).
In April, RTVE wrote to the EBU requesting a "debate" over Israeli participation amid civil society "concerns" about the situation in Gaza, where the risk of famine is rising.
Sanchez, who last year recognised a Palestinian state, also expressed on Monday "a supportive embrace for the people of Ukraine and the people of Palestine who are experiencing the injustice of war and bombardment".
At an Arab League summit in Baghdad on Saturday, the Socialist leader called for more international pressure on Israel to stop the "massacre in Gaza".
The occupied Palestinian territory has been under a complete aid blockade by Israel since March 2.
Spain will submit a proposal to the United Nations General Assembly to ask the International Court of Justice to rule on Israel's compliance with international obligations on humanitarian aid access to Gaza, Sanchez added.
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