DAP Member of Parliament Jimmy Wong said the party, instead, should focus on capturing Barisan Nasional and Umno fortresses, including the indigenous territories in the interior.
He said the fledgling party would only waste its time and resources by trying to change the mindset of voters in areas where the DAP and PKR have already long succeeded.
"They're going at the wrong direction. The (voters) in the urban areas have changed. What are they doing in trying to change the voters again? Are they thinking that the DAP and PKR have not done anything all this while?" he asked during a press conference, Monday.
He said even the DAP have been working hard in the interior areas.
Wong lamented that Warisan's attempt to fish DAP and PKR members particularly from their own ponds would only result in a disastrous outcome for the opposition camp in the coming election, as had happened in the last outing.
He recalled that in the 13th general election, the results in a number of constituencies have shown that victory would have favoured the opposition if the contesting parties had agreed to a straight fight against the ruling coalition.
He said the mistake must never be repeated this time around.
"We are not your enemy but a friend," he appealed to Parti Warisan.
Parti Warisan deputy president Darell Leiking was reported by a local daily Monday as calling all opposition parties in Sabah to be led by a common party.
The Penampang Member of Parliament welcomed parties from Pakatan Harapan to contest under the Warisan banner in the next general election.
But Wong insisted that based on the last election results, it is Parti Warisan who must learn from the experienced and tested peninsula-based opposition parties which had proven to have strong support by Sabahan voters.
He said despite the local opposition parties' widely promoted "Sabah for Sabahans" battle cry, voters still placed their votes on the DAP and PKR as credible heavyweights to match against the BN.