On July 21, the Commission had reserved its order on the issue. The next hearing will now be held on August 10.
But at the same time the poll body said while it cannot allow the applicants to be joined as parties, it may seek their assistance as offered by them, if, and when, required.
Prashant Patel, who had petitioned before the Commission seeking disqualification of the MLAs, had opposed the plea of Congress and BJP of becoming a party to the case saying "they wanted to politicise the issue".
The plea of intervention of Congress and BJP was also opposed by the 21 AAP MLAs.
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Congress and BJP had said that they should be allowed as parties as the issued involved public interest and money of the exchequer.
Since Patel and the 21 AAP MLAs are the parties assigned in the President's reference to EC, the plea of Congress, BJP and Delhi government for "impleadment as parties to the present proceedings is not maintainable before the Commission," the elaborate EC order signed by Chief Election Commissioner Nasim Zaidi and fellow Commissioners O P Rawat and A K Joti said.
Following the petition by Patel seeking their disqualification, EC had issued notices to the AAP MLAs last month.
The AAP government had appointed 21 parliamentary secretaries to assist its ministers. Subsequently, the city government sought to amend the Delhi Members of Legislative Assembly (Removal of Disqualification) Act, 1997, so as to exempt parliamentary secretaries from disqualification provisions in 'office of profit' cases.
However, the President refused to give his assent to the Bill.