He added that this principle was actually laid down to ensure that a state is represented in the Rajya Sabha in proportion to its population.

And, accordingly, even parties with smaller number of members in the state legislatures are able to elect their candidates for the Rajya Sabha, he said.

But that is possible, the lawsuit said, only when the elections for all the casual vacancies, numbering more than one, are held together through a single ballot paper, giving each member of the state legislature an opportunity to cast 'his single vote' to choose from among the candidates in the fray.

This method of holding elections together for multiple vacancies in the upper house would ensure that the largest party in the state legislature is not able to corner all the vacant seats of the house, it said.

He added that if the election for several Rajya Sabha seats are held together, even smaller parties stand a chance to get seats in the upper house.

But in case the elections are held separately with as many ballot papers as there are vacancies, each member of the house gets as many chances to vote as the number of ballot papers and this results in the largest party cornering all the seats.

This defies the principle which accords each member a single transferable vote, he added.