The new national symbol was part of a package of measures passed by referendum in August, including a new national anthem, that required a constitutional amendment – one that also abolished the country’s senate.
Senators from the ruling party of President Mohamed Ould Abdel Aziz joined opposition parties in seeking to block the measures, and the flag’s detractors made their anger clear on Tuesday.
The National Forum for Democracy and Unity, a coalition of opposition groups, called the flag “the illegitimate child of the rape of the constitution”, and said independence day was being “desecrated”.
Senator Mohamed Ould Ghadda, a main opponent of the president’s changes, was arrested on charges of “corruption” in August, prompting him to go on a hunger strike that lasted several days.
Aziz had accused senators of “treason” for failing to vote for the abolition of their chamber and for the new national anthem and flag.