Addressing a party rally at Suhrawardy Udyan in Dhaka on Sunday, she also claimed the government sent its people abroad to pressure Justice Sinha to stand down.
The president's office on Saturday confirmed receipt of Justice Sinha' resignation letter after the end of his 39-day leave.
He took the leave following criticism by the ruling Awami League for the 16th amendment verdict scrapping parliament's powers to sack top court judges on the grounds of incompetency or misconduct.
A day after he left for Australia a month ago, his colleagues in the Supreme Court said they were not eager to work with him as he had failed to explain charges of corruption against him.
"The government did not stop by driving him out of the country, it sent people from an agency abroad to pressure him to resign."
The BNP chief alleged Justice Sinha wanted to return, but he was barred.
"The chief justice spoke the truth on some issues like -- the government is controlling lower courts, it is eyeing control over the entire judiciary; the people won't get justice if this happens," she said.
"And it has become true now. It has been proved that speaking out is viwwed as a blemish. He had to resign because of speaking the truth," Khaleda said.