Why does Nepali Congress oppose fully proportional election system?

The main opposition to fully proportional election system has been none other than the biggest party of the nation Nepali Congress, why? The answer is simple as soon as it agrees on the most demanded proportional system it looses its grip to the no. of seats to the Constitutional Assembly. It has a majority of Bahun and Chhetris as its members and leaders, when it approves the system it has to leave lots of seats that equates to loss of power which is never acceptable to Congress or any other party for that matter. In this transitional phase if the biggest party is still focusing on party benefits how can we rest assure that other parties will keep the "Nation's Benefit" in their agenda?

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