London - The British government faces another nerve-rattling test this week as its flagship Brexit legislation is picked over once again by a restive parliament.
The upper House of Lords, which wants to keep Britain close to the European Union after the UK leaves in March, will rake over the EU (Withdrawal) Bill on Monday, before it returns to the lower House of Commons on Wednesday.
Last week, Prime Minister Theresa May narrowly survived votes in the Commons on changes suggested by the unelected Lords, overturning their amendment seeking to keep Britain aligned to the EU's customs union.
May also persuaded rebels in her governing centre-right Conservative Party to reject a Lords amendment that would have allowed parliament to stop the government from leaving the European Union with no deal on new trading arrangements.
But now May faces the prospect of having to go through the wringer all over again in a fresh bout of parliamentary ping-pong.
"We recognise the concerns people have about the role of parliament," May told BBC television.
But she added: "Parliament cannot tie the hands of government in negotiations."
A crunch summit of European leaders on June 28 is fast approaching, and May does not want to go to Brussels on the back of a stinging defeat in her own parliament.
- Cold sweat -
Wednesday's Commons vote required last-minute concessions, and pro-EU Conservatives warned they could yet seek to defeat May if she backtracks on promises to give parliament a greater say in the final withdrawal deal.
May is on a tightrope as her Conservative minority government relies on the backing of the 10 MPs from Northern Ireland's Democratic Unionist Party for a slim majority in the 650-seat elected Commons chamber.
And pro-EU rebels on the Conservative backbenches are proving hard for May to satisfy.
Dominic Grieve, the former attorney general who heads up the faction, told BBC television that a future vote on a Brexit deal could see May tumble.
"We could collapse the government, and I assure you I wake up at 2:00am in a cold sweat thinking about the problems that we have put on our shoulders," he said.
"The difficulty is that the Brexit process is inherently risky -- really risky."
An added risk for the pro-EU Conservative rump is that if May does fall, it could open the door for an arch-Brexiteer to take over the party, and thereby the premiership.
Notwithstanding her battles with backbenchers, May has rejected claims that divisions within her cabinet on the way forward were making negotiations with Brussels harder.
"The government has agreed that we will have an independent trade policy," she told the BBC.
"We will be free to negotiate those trade deals around the rest of the world."
She said that in the week beginning 9 July the government would set out in more detail than ever before its ambition for future relations with the EU.
- 'Arrogance and deceit' -
The Brexit talks are progressing painfully slowly, but both sides still hope to reach a deal in October ahead of Britain's withdrawal from the EU in March 2019.
May has promised to give the British parliament a vote on the final deal, but the question is what happens if lawmakers decide to reject it.
The Lords amendment overturned on Tuesday would have given parliament the power to decide whether to leave the EU if no deal is reached, keep negotiating -- or stay in the bloc.
The opposition Liberal Democrats confirmed they would support an amendment in the Lords this week to ensure parliament is given a "meaningful vote".
"Theresa May's plans are nothing if not breathtaking in their arrogance and deceit," said Dick Newby, their leader in the Lords.
"The government's current proposal would neuter parliament if the government failed to reach a Brexit deal.
"Parliament must be given a meaningful vote on all possible outcomes of Brexit -- and this must be guaranteed in writing."
The EU (Withdrawal) Bill would formally end Britain's membership of the bloc and transfer more than 40 years of European law on to the British statute books.
By Robin Millard