The pledge came at the procession organised by the party on Sunday in the capital in celebration of the 46th Victory Day.
Thousands of party activists, supporters and leaders took part in the parade that marched from Naya Paltan party offices to Mouchak.
They carried colourful festoons, balloons, banners, placards and portraits of party leaders while the musical band played the national anthem and patriotic songs.
The supporters shouted slogans for Bangladesh, the country's victory and independence, and for their late leader Ziaur Rahman and current chief Khaleda Zia and her son Tarique Rahman.
At the beginning of the parade, BNP Secretary General Mirza Fakhrul Islam Alamgir addressed the party followers from a makeshift dais on a truck.
"We want to say, you cannot subdue the people's will by stifling them; you cannot keep the people supressed," he added.
He called on the BNP activists to take part in the procession peacefully to press the demand for ‘bringing back democracy by forging national unity’.
BNP Senior Joint Secretary General Ruhul Kabir Rizvi also addressed the rally.
Among others, BNP Standing Committee members Khandaker Mosharraf Hossain and Amir Khosru Mahmud Chowdhury, Vice Chairmen Shamsuzzaman Dudu and Ahmed Azam Khan, and party chief's Advisory Council members Amanullah Aman, Abdus Salam and Habibur Rahman were present at the programme.