Bihar Chief Minister Nitish Kumar had defended the boycott of the function.
JD(U) chief spokesman Neeraj Kumar on Monday lashed out at Rajya Sabha Deputy Chairman Harivansh for taking part in the inauguration of the new Parliament building despite boycott of the function by the party.
In a strongly worded statement, Mr Kumar deplored the journalist-turned-politician's participation in a function where "even your Chairman, the Honourable Vice President, was not present".
"The party had sent you to the Rajya Sabha in recognition of your contributions to journalism. But when a dark chapter in the history of parliamentary democracy in the country, you traded intellectual integrity for your high office", said the JD(U) spokesman.
Bihar Chief Minister Nitish Kumar, the party's supreme leader, had defended the boycott of the function terming it as "an attempt to change history by those who had made no contribution to the freedom struggle".
More than 20 parties opposed to the BJP had boycotted Sunday's function, insisting that President Draupadi Murmu, and not Prime Minister Narendra Modi, should have inaugurated the new building.
The JD(U) spokesman added "It is for the top leadership to decide what action to take in view of your participation despite the party having decided to boycott. But future generations will what to make of your action that was unbecoming of a person of your stature".
Serving his second consecutive tenure in the Rajya Sabha, which will end next year, Harivansh has been the Deputy Chairman since 2018, when he became only the third non-Congress MP to occupy the post.
The 66 years old had served as a media advisor to the then Prime Minister Chandra Shekhar before serving as editor of Prabhat Khabar, one of the leading Hindi newspapers of Jharkhand and Bihar.
The JD(U) pulled out of the BJP-led NDA last year and has since been a part of 'Mahagathbandhan', which includes RJD, Congress and the Left.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)