Ahmad Zahid Hamidi has warned that a continuous split within Umno will lead to its collapse.
The Umno president urged party leaders to accept their current situation and not think about saving their own skins.
"In times of defeat, when the party is down, there are those who do not think about what is good for the party, but how to save themselves from being investigated (and) being prosecuted.
"That means we are not steadfast, because we think it is us who need saving, and not the party," Umno Online quoted Zahid saying in his speech at a retreat in Temerloh.
Zahid, the former deputy prime minister, added that a number of ulama he met told him that Umno's loss in the 14th general election was to facilitate a "cleansing process."
He added that Umno should use its ammunition on its opponents, and not those within the party.
Taking a note from history, he pointed out that "insiders" played a role in Dutch colonial rule in Malacca, the signing of Pangkor Treaty which paved the way for British imperialism in Malaya, as well as the Communist insurgency.
"Umno does not rely on a single leader. It is formed on a hierarchy and the performance of the leadership, and that's Umno's real strength," he said.
Zahid has come under calls to step down amid the mass resignations of Umno MPs and assemblypersons of late.
The majority of those who quit have blamed him for failing to chart a direction for the party following its electoral defeat.
Umno was the largest party in the Dewan Rakyat with 54 MPs despite losing power in the 14th general election.
However, it is now left with just 38 MPs after the exodus.