Ten others, including his bodyguards, were wounded in the shooting.
But Maheshwaran had not asked for enhanced personnel protection, Defence Ministry secretary Gothabhaya Rajapakse, who is also President Mahinda Rajapakse's brother, told our sister news website, Vimasuma.com.
Rajapakse said had any lawmaker done so, the request would have been considered.
Earlier Tissa Attanayake, general secretary of the UNP, charged that authorities had recently reduced Maheshwaran's security.
Rajapakse also said the military has to give preference to deploying troops to fight the Tamil Tigers rather than using them to give security to parliamentarians.
Maheswaran has survived an earlier assassination attempt by Tamil Tigers, but he has recently been critical of the government.
The government intends to intensify its m