"Ultra-rightist and ultra-leftist forces are placing various obstacles on the way to promulgating the constitution," he said.
Poudyal was addressing a workers' training programme here organised on the 91st birth anniversary of former Prime Minister and veteran leader Girija Prasad Koirala.
Monarchists and Communist forces have joined hands to sideline democratic forces and to weaken democratisation since the establishment of democracy in 1950, he said.
"The pro-rightist and pro-leftist forces could never accept the democratic changes that have taken place in Nepal since 1950," Poudyal said.
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The country is still facing a chaotic situation due to the unholy alliance between the two extreme forces of the national politics, he added.
They were raising ultra nationalist and progressive slogans to deceive the people, he said.
He also underlined the need for revamping the organisational structure of the largest democratic party, even as it succeeded in emerging as the largest party in last year's Constituent Assembly elections.
But he had clearly mentioned that he would not be obliged to support monarchy if it does not accept democracy," he said.
"And overthrowing of monarchy in 2008 after King Gyanendra took absolute powers by suspending democracy was not against the principle adopted by late Koirala," he made it clear.
Nepali Congress is committed to promulgating a full-fledged democratic constitution within the next six month as per its commitment made during the Constituent Assembly elections last year, Poudyal said.