Describing the setback suffered by her party in the by-elections as very disappointing, Congress president Sonia Gandhi on Tuesday said she has asked her party colleagues to take corrective measures.

The Congress lost Solapur (Maharashtra) and Ernakulum (Kerala) parliamentary seats in the by-elections held last week and emerged third in the assembly by-elections in Meghalaya, West Bengal and Orissa.

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The defeat in Solapur in Maharashtra, where the party has the largest number of Lok Sabha seats, brought to fore the simmering differences between Congress and its major ally Nationalist Congress Party.

The NCP had reportedly refrained from canvassing for the Congress candidate in Solapur, which was considered as one of the factors for the party's defeat.

NCP president Sharad Pawar had reportedly admitted that his partymen might have canvassed for the BJP nominee, Pratapsinh Mohite-Patil, younger brother of NCP MLA and PWD Minister Vijaysinh Mohite-Patil.

However, Shinde ruled out any adverse fallout on the relationship between the Congress and NCP, and on his government.

Shinde represented Solapur seat before taking over as chief minister.

In Mumbai, the Bharatiya Janata Party questioning Chief Minister Sushilkumar Shinde's right to lead the ruling coalition during next year's assembly elections when he could not ensure victory of a Congress nominee on his home turf.

BJP's Maharashtra unit president Gopinath Munde said Shinde's continuance at the helm of the affairs would make things easy for the opposition Shiv Sena-BJP combine.

In Kerala, the Communist Party of India-Marxist appeared to dangle a bait of doing business with senior Congress leader K Karunakaran even as the ruling United Democratic Front's key ally Indian Union Muslim League remained non-committal on a leadership change in the state.

CPI-M state secretary Pinarayi Vijayan, attending a meeting of the party's central committee in Delhi to discuss the fallout of the Lok Sabha by-poll, indicated that his party would lend outside support to a Karunakaran-led alternative dispensation.

Asked if the CPI-M would cooperate with Karunakaran if he quit the Congress, Vijayan said his party had allied with Chief Minister A K Antony when he had left the Congress in 1980 and "if the situation warrants, we will take a positive step." It was 'circumstances' and not 'individuals' that mattered.

Reducing Antony's comfort level, IUML general secretary E Ahmed, when asked about the party's stand on Karunakaran's demand for a leadership change, did not come out in emphatic support of the chief minister and instead said the League would spell out its stand when such a situation arose.