Bill would repeal the European Communities Act 1972 and ensure that EU-derived legislation having effect on domestic law remains in force on and after "exit day".
Liberty director Martha Spurrier said: "If the Repeal Bill passes in this state, people in the United Kingdom will lose rights after we leave the EU".
Britain duly outlined its stance on nuclear materials and there was also a paper on judicial matters - a significant hurdle as London and Brussels disagree on whether the European Court of Justice will continue to have jurisdiction.
"If the European Union genuinely want to resolve the question of residence rights of European Union nationals, they need to separate out the two issues to enable a negotiation in good faith which can give certainty to the hundreds of thousands of children and their families left in limbo".
Some EU laws, known as regulations, are now automatically applicable to Britain without having required domestic laws to be passed.
Professor of European politics in London, Anand Menon told Larry Williams the bill is critical to Brexit. Then, if needed, they can be changed within a two-year window from exit day - in order to correct any "deficiencies".
The publication of the new Bill follows the government's "white paper" earlier this year which set out a three-point plan for converting European Union law into domestic law at the point that Brexit takes effect.
However, the bill would give the government new powers to alter up to 1,000 different regulations for up to two years, known as "Henry VIII powers". However, this requirement will not apply in cases the Government considers "urgent".
The medieval powers, which give the Government the right to change the law at the stroke of a pen, are set to spark intense opposition from both MPs and peers opposed to an "extreme Brexit".
However, the Bill provides government ministers with the power to introduce new regulations before the United Kingdom parliament to challenge the validity of retained European Union law.
Given May's governing Conservative Party does not have a majority in parliament, any parliamentary challenge is a potentially serious threat to the government.
The publication of the Bill is the first step in a long legislative process. But it was never likely to be the official title of the Bill in reality. "Any attempt to use Brexit and the Repeal Bill as a backdoor means to avoiding implementation of the highest standards would be hugely irresponsible in an era of superbugs".
It will be essential for businesses to be alive to the detail of regulations made under the Bill to ensure that their interests are protected in a fast moving environment.
'We must make sure that in the process hard won rights are not lost, ' Egan said. Removing it has, however, given Labour an attractive rallying point for opposition to the Bill and an argument that it is more than the technocratic exercise the government claims.
Others accused Downing Street of a "power grab" after it emerged the Government will use "Henry VIII powers" set down in 1539 to rush the legislation through without it being probed by Parliament.