New Delhi (PTI): Describing the electoral tie-up between the Congress and Trinamool Congress as "unholy", Left parties on Monday put up a brave front saying there were formal or informal alliances during earlier elections too.

"Even if there was no official alliance, the two parties have tied up at the ground level on earlier occasions too. We have faced it then, we will face it now again," CPI(M) Polit Bureau member Sitaram Yechury said here.

His party colleague Nilotpal Basu said the tie-up was "an unholy gang-up of anti-Left forces" while Yechury said the Congress had joined hands with an alliance which has forces from the extreme Right to the extreme Left.

The Congress would have to explain "why it has joined hands with forces supporting the Left extremists, to control whom Home Minister P Chidambaram had to convene high-level meetings. The Congress would also have to explain why it has tied up with those who opposed development", Yechury said.

On the Trinamool Congress, he said this party had earlier joined hands with Congress, "then its chief (Mamata Banerjee) tendered a public apology and then continued her alliance with BJP. Now she has once again aligned with the Congress".

To questions on Left joining hands with non-BJP, non- Congress parties, Yechury said the CPI(M) Central Committee would meet this weekend to take a final view.