Its closest rival remained Hyundai Motors India Ltd with a 15.18% share, while Mahindra & Mahindra (10.15%) overtook Tata Motors (7.94%) to the third spot.
Japanese major Honda was in fifth place with a market share of 5.36%, just ahead of Toyota's 5.14%.
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Domestic sales of passenger vehicles, which includes cars, utility vehicles and vans, declined 6.05% to 25,03,685 units in the previous financial year from 26,65,015 units in 2012-13, according to data from the Society of Indian Automobile Manufacturers (SIAM).
Maruti's market share increased from 39.43% in 2012-13, when Hyundai's was 14.39%, Mahindra's was 11.65% and Tata Motors 11.79%.
During FY14, Maruti's passenger vehicle sales grew marginally to 10,53,689 units from 10,51,046 units in 2012-13. Hyundai sold 3,80,253 units in FY14 against 3,83,611 units in FY13.
Mahindra's passenger vehicle sales were down 18.14% to 2,54,344 units from 3,10,706 units.
Tata Motors sold 1,98,812 passenger vehicles in FY14, a drop of 36.77% from 314,464 units.
Honda Cars India, which had a good year riding on its compact sedan Amaze and the new City model, posted growth of 82.81% to 1,34,339 units.
Toyota Kirloskar Motor, which has been hit by labour unrest at its two plants in Bangalore, sold 1,28,811 units in 2013-14, down 22.17%.
In the car segment, Maruti's sales in FY14 grew 3.38% to 8,90,455 units, while that of Hyundai was down 0.86% to 379,555 units.
Honda's car sales zoomed 82.17% to 1,33,321 units, while those of Tata Motors fell 38.64% to 1,07,187 units.
Toyota Kirloskar's car sales were down 21% at 56,865 units.
During the previous financial year, Mahindra's sales of utility vehicles dropped 16.86% to 2,19,421 units.
In the motorcycle segment, market leader Hero MotoCorp's sales grew 1.16% to 54,25,118 units in 2013-14 from 53,62,730 units a year earlier.