The leader of opposition said people of the state have lost confidence in the police and investigating agencies.
"Ever since the Congress has come to power, the law-and- order situation in the state has deteriorated. Criminals and anti-social elements have no fear of the law," Dhumal told reporters.
He suggested that the government should have immediately accepted the demand of the victim's family for the CBI probe.
"How can a person consume poison and climb the tree in a forest?" he asked.
Singh's body was found hanging from a tree in the forest of Karsog area in Mandi district on June 9.