In a media briefing on Wednesday, she, however, did not announce any programme though the former prime minister had been demanding that the project be scrapped altogether.
Bangladesh has signed a deal with India to set up the 1,300-megawatt thermal power plant.
The two countries will have equal partnership in the venture styled Bangladesh-India Friendship Power Company Ltd.
Leftist parties have been opposing it saying that the coal-fired power plant will threaten the ecological balance of the Sundarbans, the largest mangrove forest of the world.
The government, however, insists that proper measures will be taken to protect the environment from pollution.
Flanked by top leaders of stakeholders of her 20-Party coalition, Khaleda told the media, "The autocratic government has disregarded the people's opinion and is imposing its decision about the power plant on them."
“We think there are many more alternatives to generating power. There are also alternatives places to set up power plants. But there is no alternative to the Sundarbans,” she said.
“So we strongly demand that the government cancel all the thoughtless, irrational and unprofitable coal power plants, including Rampal power plant, that are confirming the destruction of the Sundarbans.”
Khaleda called on the people to build a movement against the Rampal power plant.
The BNP chief, in her 30-minute speech to the media after one and a half months, pointed out the harmful sides of the plant.
She urged the media to highlight these in reports but did not take questions from journalists.
The partners in the BNP-led alliance agreed to launch a movement against Rampal plant last week, Jatiya Ganatantrik Party chief Shafiul Alam Prodhan had said.