A tie-up between Umno and PAS would not help BN and instead drive non-Malay voters towards Pakatan Harapan, said MCA deputy president Wee Ka Siong.
In a statement today, Wee said 85 out of 222 parliamentary seats in Malaysia consist of more than 35 percent Chinese and Indian voters.
"If Umno chooses to work together with PAS, BN can kiss these constituencies goodbye. A PAS-Umno cooperation is also not feasible for the 56 seats in Sarawak and Sabah.
"In politics, one plus one does not always equal two. The elections in Taiwan and Indonesia have shown that support for Party A and Party B does not necessarily add up when A and B collaborate.
"So please do not assume that respective support for Umno and PAS would automatically combine when a PAS-Umno pact is established," said Wee.
Wee said Chinese and Indian voters snubbed BN during the May 9 general elections because they believed Umno was authoritarian and racist.
"To quote former Umno Youth chief Khairy Jamaluddin, Umno should steer away from racial politics and focus on socio-economic issues.
"Initiate constructive discourse on the economy, tax system, cost of living, transportation, among others, to keep Pakatan Harapan on their toes and to contribute meaningfully to nation building.
"Otherwise, there will be no rebound for that party," said Wee.
Wee's assessment for BN comes at a time when Umno and PAS are actively seeking to forge a political alliance.
Both parties campaigned for one another during recent by-elections and have pledged to send representatives to their respective annual delegate meetings.
Previously, Wee and MCA president Liow Tiong Lai have both stated that MCA was independent of BN and will no longer carry Umno's baggage.