The security lapse during the visit of Prime Minister Manmohan Singh [Images] at Thiruvananthapuram should not be taken lightly and was a great failure on the part of the government and police officials, opposition leader Oommen Chandy said on Friday.

Speaking to reporters, he welcomed Chief Minister V S Achuthanadan's directions to Chief Secretary Lizzie Jacob to inquire into it.

The incident had occurred, despite a trial run for the motorcade being held four times following the e-mail threat to the prime minister.

"This is a great disrespect to the state," he said.

The government has violated protocol by appointing a taxi driver instead of hiring the services of someone from the police department or Raj Bhavan, Chandy said.