The Left parties on Sunday strongly criticised the coming together of the Bharatiya Janata Party and Janata Dal (S) to form a government in Karnataka, saying their "rank opportunism" have betrayed the people's aspirations in Karnataka.

"The rank opportunism of the Janata Dal (S) leadership and the unprincipled lust for power of the BJP have betrayed the aspirations of the people of Karnataka," the CPM's politburo said in a statement.

The party favoured holding of fresh elections in the state.

"There is nothing to be gained from such exercise. The only sensible and democratic way out is for the state to have fresh elections," it said.

Reacting to the development in the state, the CPI said the door for the BJP to get a foothold in the southern states has been opened which was very "unfortunate".

"The attempt to install a BJP-led government in Karnataka, with the help of the JD(S) is a serious and unfortunate development," the party said in statement.

"It will add to communal tension in Karnataka where in the past the BJP and the VHP have made several attempts to inject the communal poison, and about which only a few days ago the JD(S) leadership had charged the BJP with wanting to repeat a Gujarat in Karnataka," it said.

Both the parties also condemned the Maoists attack in Jharkhand which claimed 17 lives, including the son of former chief minister Babulal Marandi.

"The Centre should immediately draw up a plan for coordinated action by the security forces in Jharkhand and Chattisgarh," the CPM said.