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Arvind Kejriwal's Aam Aadmi Party contends that the 20 lawmakers were not allowed to present a defense. The party also insists that the lawmakers drew no salary or perks as parliamentary secretaries and so there is no question of their having held offices of profit.
According to the provisions of office of profit, elected representatives are not allowed to hold positions of pay and perks in the government without specific laws that allow them to do so. A government post is also considered out of bounds for lawmakers because they could then skew towards the executive.
The Election Commission said that by serving as parliamentary secretaries in absence of a law allowing it, the lawmakers had violated office of profit provisions. The Commission also said the AAP lawmakers skipped several chances to defend itself.
Parliamentary secretaries assist ministers. Several states like Madhya Pradesh and Rajasthan have amended laws that allow lawmakers to perform this function.
In 2015, Mr Kejriwal appointed 21 AAP lawmakers as parliamentary secretaries. A lawyer and later, the Congress, petitioned the Election Commission to disqualify them.
The High Court later cancelled the appointments as they had not been cleared by Delhi's Lieutenant Governor, the capital's administrative head. One of the MLAs resigned last year.
Sacking of the 20 lawmakers does not dent the majority of Arvind Kejriwal, whose party holds 66 of Delhi's 70 seats, comfortably above the halfway mark of 35. But a by-election in 20 seats -- more than a third in the assembly -- would practically mean a mini-election.
AAP has recently lost a string of elections including for municipal bodies. A bad result would weaken Mr Kejriwal's moral and political authority at a time when his party is seen as vulnerable to fissures after his falling out with another popular leader, Kumar Vishwas.
Senior AAP leaders say the Election Commission is acting on behalf of the BJP in a blatant misuse of power. The party has also said it would go to the Supreme Court if need be.
Mr Kejriwal's key lieutenant, senior party leader Ashutosh has called the President's nod to Election Commission's recommendation "unconstitutional and dangerous for democracy".