Chief presidential secretary for political affairs Jun Byung-hun said Wednesday he opposes the integration of the ruling Democratic Party of Korea (DPK) and the People's Party.
"There should be no artificial political realignment," Jun said during a radio interview. "This would only cause severe conflicts between the existing parties."
He said integrating the liberal parties would prompt political chaos.
"I believe the people hope to see the existing parties strive for cooperative politics in the current five-party system," he said.
Political realignment has been one of the key parliamentary issues under the Moon Jae-in government.
Moon's DPK, which does not have an absolute majority in the 299-seat legislature, has been thought to be seeking a merger or alliance with the People's Party, which originally formed when lawmakers exited the leading liberal party. The 120-seat DPK can get a majority with the support of the 40-seat People's Party.
But talks on political realignment appeared to be losing momentum. Jun's comment is in line with the present parliamentary situation, according to pundits.
The DPK passed a supplementary budget bill with the backing of the People's Party and the Bareun Party on Saturday. Party leaders are gradually warming to a strategy of embracing the two minor opposition parties while isolating the main opposition Liberty Korea Party (LKP), party officials said.
They are also aware of the possibility that an alliance with the People's Party would spur the remaining opposition parties to join hands, escalating tensions and fueling the power game between the ruling party and opposition bloc.
Speculation is also growing that the People's Party may survive the fallout of the fabrication scandal. With the prosecution expected to wrap up its investigation soon, the involvement of party leaders has yet to be proven.
Following the scandal involving a party member who fabricated evidence used in the party's presidential campaign to smear President Moon Jae-in, the party's approval rating plummeted in its Jeolla region stronghold.
Political watchers have said the party could be embroiled in a political realignment, especially if the party leaders are found to be involved in the scandal.