The BJP has the maximum of 82 members and the Congress 46 in the Rajya Sabha, which has a total strength of 245.
The opposition strength in Rajya Sabha is set to reduce further as the Congress is expected to lose some of its seats in elections slated for later this year to fill up 68 vacancies.
According to sources, the Congress could lose around nine of its 19 seats that are falling vacant due to its reduced strength in some states, amid speculation that the party is contemplating bringing in some bigwigs, including Priyanka Gandhi Vadra, Jyotiraditya Scindia and Randeep Surjewala, to the upper house.
The Congress is confident of retaining nine seats on its own and winning one or two more with the help of its allies.
The party is set to gain seats in states where it is in power — Chhattisgarh, Madhya Pradesh, Rajasthan and Maharashtra.
The opposition strength will fall after elections are held to fill up 68 vacancies in April, June and November, that may lead to the ruling NDA slowly inching towards the majority mark of in the upper house, sources say.
While 51 seats in Rajya Sabha are falling vacant in April, five more in June, one in July and 11 in November this year.
Top Congress leaders Motilal Vora, Madhusudan Mistry, Kumari Selja, Digvijaya Singh, B K Hariprasad and MV Rajeev Gowda are among the top Congress leaders whose tenures are ending in April and June.
Of them, Vora, Selja and Digvijaya Singh are likely to be renominated by the party.
Besides, its leaders Raj Babbar and PL Punia are unlikely to get renominated from Uttarakhand and Uttar Pradesh, where the ruling BJP is set to make major gains. One RS seat in Uttarakhand and 10 seats in Uttar Pradesh are falling vacant in November this year.
A large number of Congress leaders are vying to get a Rajya Sabha seat from the party after a large number of them lost out in the last Lok Sabha elections and there is speculation that the party may bring Priyanka Gandhi, Jyotiraditya Scindia, Randeep Surjewala and RPN Singh, among others, to the upper house.
There are six vacancies coming up in Maharashtra, including that of NCP supremo Sharad Pawar, and the same number in Tamil Nadu, while there are five each falling vacant in West Bengal and Bihar, four each in Gujarat, Karnataka and Andhra Pradesh.
The Congress is likely to bag two of the three seats in Rajasthan, two of three in Madhya Pradesh, two in Chhattisgarh, one in Maharashtra and one in Karnataka. The party will lose seats in Karnataka, Andhra Pradesh, Telangana, Meghalaya and Assam.
The ruling NDA does not have a majority in the Rajya Sabha and the government has to seek the support of friendly parties such as the AIADMK and BJD to get crucial legislations passed in the upper house.
The BJP has the maximum of 82 members and the Congress 46 in the Rajya Sabha, which has a total strength of 245. There are 12 nominated members in the upper house, eight of whom have aligned with the BJP.
Uttar Pradesh has the maximum representation of 31 members in the Council of States, followed by 19 MPs from Maharashtra, 18 members from Tamil Nadu and 16 MPs from West Bengal.