The Supreme Court on Monday described as a "mockery" and a "murder of democracy" last month's Chandigarh mayoral polls, won by the BJP candidate, after watching video footage of the election and accusing the returning officer of tampering with ballots.

The BJP's Manoj Sonkar was declared the winner against the joint AAP-Congress candidate, Kuldeep Kumar, in the January 30 election after eight votes were declared invalid by returning officer Anil Masih.

"It is obvious he (returning officer) has defaced the ballot papers…. We are simply appalled by what he is doing. Is this the way an election is conducted by a returning officer?... The man defaces ballots the moment he sees a cross at the bottom," Chief Justice D.Y. Chandrachud said.

"This is a mockery of democracy. We are appalled by what has happened. We will not allow democracy to be murdered like this. This is nothing but murder of democracy," he told solicitor-general Tushar Mehta, appearing for the returning officer, and senior advocate Maninder Singh, who was representing the Union Territory of Chandigarh.

Justice Chandrachud orally observed: "Tell your returning officer that the Supreme Court is watching over him. We will not allow democracy to be murdered like this."