A former judge of the European Court of Justice has criticised the “facile optimism” of UK government ministers who believe the legal challenges posed by Brexit can be overcome by March 2019.

Speaking to Scotland on Sunday, Sir David Edward said the Great Repeal Bill was “full of gaps” and could not deal with the legal complexities of leaving the EU.

Sir David said: “The Brexit Bill demonstrates that the true ghastliness of the legal problems is unimaginable.

“It is just facile optimism to imagine that all the legal obstacles and problems can be overcome in this way and in this timescale.”

He continued: “The Bill is full of gaps. The basic problem is that the British government has failed to understand that the EU treaties are not normal international treaties. They create a complex skein of reciprocal rights and obligations for the member states and their nationals – including companies and partnerships as well as individuals.

“It is not just a matter of converting treaty rights and obligations into British law. For example, the rights of other EU nationals in this country are exactly the same as the rights of British nationals in other member states, and you can’t reproduce that mirror image of rights simply by changing British law.”

He said many rights for citizens across the EU are tied in with the freedom of movement of goods, people, services and capital.

Sir David said: “For example, the local representatives of British companies in Germany can take their spouse or partner and children, and even grandparents if they are dependent on the family. They are all entitled to education, social security and health facilities.

“They have a right to remain in Germany and their rights are the same as those of the representative of a German company in Britain.

“The British government proceeds on the assumption that this is an intergovernmental issue. It is not. Governments can’t trade the rights of EU citizens for access to bully beef.”

A spokesperson for the UK government’s Department for Exiting the European Union insisted the purpose of the Bill is “to make sure the law continues to work properly on the day we leave the European Union”.

She added: “It means we will have a functioning statute book, and ensures that our sovereign parliament, and in some cases the devolved legislatures, can make any future changes.

“The Repeal Bill means the UK will be able to exit the EU with certainty, continuity and control. That is what the British people voted for and that is what we will deliver.”