Driven by smart December quarter earnings, IT major Tata Consultancy Services has become the country's second largest firm in terms of market valuation, lagging behind corporate leader Reliance Industries.

TCS, which was the top gainer among the country's 10 most valuable companies in the last week, saw its valuation surging by Rs 18,378.11 crore to Rs 2,37,330 crore in the week.

State-run ONGC slipped to the third position after its valuation dipped by Rs 15,763.47 crore -- the most among top 10 companies -- to Rs 2,36,355.83 crore during the week.

Mukesh Ambani-led RIL, the country's most valuable firm, lost Rs 4,794.78 crore in mcap in the week. Its valuation was Rs 3,22,870.6 crore as on Friday last week.

The country's largest software firm, TCS, last week posted 29.93 per cent growth in consolidated net profit at Rs 2,369.83 crore for the October-December quarter.

Boosted by the smart earnings, shares of the company advanced by 8.39 per cent during the week to Rs 1,212.60 on the Bombay Stock Exchange as on last Friday.

Analysts said that improvement in operating margins was a pleasant surprise for the market from TCS.

"With the kind of growth TCS has displayed in its quarterly earnings, the company is better positioned than its peers. Becoming the country's second largest firm is a remarkable achievement. TCS has benefited from the laggardness of ONGC," SMC Global Securities Strategist and Head of Research Jagannadham Thunuguntla said.

During the period, six firms, including TCS, SBI and ICICI Bank posted gains. The market capitalisation of six of these firms grew by Rs 38,210.98 crore.

Two of the top lenders, SBI and ICICI Bank, together added Rs 12,437 crore to their combined market capitalisation.

The m-cap of SBI stood at Rs 1,64,967.23 crore, while that of ICICI was at Rs 1,22,429.93 crore.

IT bellwether Infosys Technologies also added Rs 2,686.89 crore to take its valuation to Rs 1,86,517.24 crore.

State-run Coal India's m-cap also swelled by Rs 2,400.21 crore to Rs 1,98,302.12 crore.

Similarly, NTPC's market worth too surged by Rs 2,308.73 crore to Rs 1,56,333.92 crore.

FMCG giant ITC also saw an erosion of Rs 910.54 crore from its m-cap which was at Rs 1,30,282.41 crore, while telecom player Bharti Airtel's m-cap eroded by Rs 2,316.49 crore to Rs 1,27,824.52 crore.