"The people of the country know what's what and they will reject the BJP ideology as the result in Karnataka shows," he told reporters.
Manmohan Singh admitted that corruption "is a major issue in the country" and suggested that all sections of society sit together and find a solution to this problem.
The prime minister said Congress vice president Rahul Gandhi "took a leading role" in the Karnataka campaign "and worked hard".
"I congratulate the Congress workers of Karnataka."
The Congress is set to return to power in Karnataka with a simple majority in the assembly. The BJP was routed.