What are the challenges and controversies surrounding the Brexit Bill?

Theresa May's Brexit strategy is facing one of its toughest challenges as the EU (Withdrawal) Bill goes through the committee stage in the House of Commons.

Here are some of the facts about the Bill.

What does the EU (Withdrawal) Bill aim to do?

Originally known by ministers as the Great Repeal Bill, the legislation repeals the 1972 Act which took the UK into what was then the European Economic Community. It will also transpose all relevant EU rules and regulations onto the UK statute book.

What is the committee stage?

This is the point in every bill's passage through Parliament when it is subjected to line-by-line scrutiny, usually by a group of a few dozen MPs sitting on a Public Bill Committee. Like other major pieces of legislation, the Withdrawal Bill is being dealt with by a Committee of the Whole House, allowing all MPs to debate and vote on its provisions in the Commons chamber.

Why does the Government want to keep EU laws after Brexit?

Ministers are keen to ensure a "smooth and orderly" departure. And they are also keenly aware of the tight timetable to get ready for life outside the EU, which does not allow time to rewrite all the laws the UK has signed up to in 44 years of membership. By keeping EU rules, they hope to ensure that there are no gaps in British law immediately after Brexit. And they hope that continuity in the legal and regulatory framework will maximise the chances of a close trading relationship. Parliament will then be able to go through the EU-derived rules over the coming years and "amend, repeal or improve" them where necessary.

Will it be a straightforward process?

Far from it. The total body of EU law - known as the acquis communautaire - amounts to around 80,000 items, many of which make specific reference to EU institutions and procedures which will no longer apply to the UK after Brexit. Officials will have to go through thousands of documents with a fine-toothed comb looking for details which need amendment.

How can the Government amend the rules while putting them into British law?

This is one of the most controversial aspects of the Bill, which envisages ministers making potentially thousands of minor corrections without parliamentary debate through what are known as Henry VIII powers. Critics claim that this allows the Government unprecedented scope to change the law without adequate scrutiny.

Is this the only subject of controversy?

No. Many MPs are also determined to ensure that the Bill allows Parliament a "meaningful" vote on any final Brexit deal - and on the possibility that Britain might leave the EU without a deal. Brexit Secretary David Davis promised a separate bill on Monday to give MPs a vote. But critics say his concession does not go far enough, as they will be offered only the choice of the agreement secured by the Government or a "no deal" Brexit and will not be offered the options of voting to remain in the EU or to send ministers back to renegotiate.

Are those the only challenges to the Bill tabled by the Government?

No. MPs have put down almost 500 amendments. Not all of these will be put to a vote, but there will be plenty of opportunities for Government defeats. One key issue is the date and time of Brexit itself, with MPs including former attorney general Dominic Grieve objecting to Mrs May's plan to enshrine it in law at 11pm on March 29 2019.

How long is this all going to take?

Eight days have been scheduled for the committee stage, with the first two taking place on Tuesday and Wednesday of this week. No schedule is yet in place for the remaining six, when the most contentious debates are expected.The Bill must then come back to the Commons for report stage and third reading, before heading to the Lords, where it is likely to face tough scrutiny. Any significant amendments there could result in a bout of "parliamentary ping-pong" as the Commons attempts to exert its authority over the final shape of the legislation. The Government needs the Bill to complete its passage through both Houses before Brexit.

Is Theresa May guaranteed to get her way?

Not at all. Without an overall majority in the Commons, the Prime Minister is vulnerable to rebellions by Tory backbenchers, some of whom have grave misgivings about the whole Brexit process. Even with the Democratic Unionist Party's pledge of support from its 10 MPs, a rebellion by any more than half a dozen Tory MPs could put Mrs May's majority in peril. In practice, however, some Brexit-backing Labour MPs can be expected to vote with the Government, and it is unlikely that Jeremy Corbyn would want to infuriate millions of Leave-backing Labour voters by blocking the Bill.

Would Brexit be halted if the Bill is blocked?

No. The terms of Article 50 of the EU treaties make clear that a member state leaves two years after issuing notification of its intention to quit, which for the UK is March 29 2019. Without this Bill, however, the impact of leaving would be far more unpredictable and potentially chaotic.