Deputy head of the Bangladesh Nationalist Party (BNP), Fakhrul Islam Alamgir, told the rally of up to 15,000 people at the capital's Suhrawardy Udyan memorial that his party would not take part in any polls under the incumbent government.
"There will be no polls without caretaker government," he said to loud cheers, adding that the party would continue demonstrations until the government restores a neutral caretaker system of government during election time.
The next general election is due in January 2014.
The rally was the first by the opposition after the government on May 19 slapped a ban on political meetings and gatherings for a month in the wake of deadly protests by Islamists that left dozens of people dead.
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Home Minister Muhiuddin Khan told reporters at the time that the government "will not allow any parties to hold rallies in the next one month" in line with a bid to curb political violence.
"It was peaceful," he said, adding that the Dhaka Metropolitan Police had approved the rally, but that he was unsure whether it meant that the government ban had been lifted.