The plans are part of the Criminal Justice and Sentencing Reform Bill, which will be introduced in the Queen's Speech on 13 November and published three weeks later.
Policy officer Gareth Crossman said Liberty agrees with aspects of the Bill, but regards plans to reveal defendants' past convictions to juries as a mistake, since it entails the added danger of increasing the risk of wrongful convictions. 'This is by far the most important issue we will face in the coming months,' he said.
Liberty is planning a concerted lobbying push, which will target MPs and peers.
The organisation is talking to other pressure groups and court user groups about releasing a joint statement of concern.