The pound rebounded slightly on Wednesday after Prime Minister Theresa May announced she would hold a parliamentary debate on Brexit proceedings and promised to fight for "maximum possible" access to European Union markets.
Miller, wants parliament to legislate on the terms of Brexit before May can trigger Article 50 of the EU's Lisbon Treaty - starting the formal procedure for leaving the European Union.
A leaked British government report said Tuesday that a "hard Brexit" - Britain leaving the single market - could lose the country up to $81 billion a year.
But in a bid to head off a Conservative revolt, May has promised that lawmakers will get a say, as long as it "does not undermine the negotiating position of the government".
He also said that while he will in the future be "pressing for a vote" on the government's Brexit terms, Labour's motion on Wednesday was meant to ensure parliamentary scrutiny rather than secure a vote.
The party has also given the government 170 questions on the detail of the Brexit plan - one for every day until the end of March, the deadline May has set for triggering Article 50.
Challenged at Prime Minister's Questions, Mrs May insisted suggestions that Parliament would be unable to debate issues around Brexit were "completely wrong".
Former minister Claire Perry said she was "extremely concerned" about the pound's overall poor performance over the past week while Chris Philp asked for as much clarity as possible over likely future trading arrangements. Leaked Treasury papers this week suggested leaving the single market could cost the United Kingdom £66 billion ($80.4 billion) in lost tax revenues.
But few have voiced it lately as May has insisted she will honour the popular will, even though she campaigned with predecessor David Cameron to stay in the EU.
But despite the political sensitivities, McFarlane believes British Prime Minister Theresa May and her Brexit ministers are privately motivated to secure a favourable trade deal for the industry to protect a vital source of tax receipts.
"In my opinion, the only real alternative to a "hard Brexit" is "no Brexit".
Conservative MP Bernard Jenkin, said there are "great many people" involved in the case who aim to block Brexit or "maintain a half in, half out solution". On Tuesday, several senior bankers said they could start moving staff overseas as early as next year if there was no clarity on access to the single market.
European Union leaders have said Britain must accept free movement of people if it wants continued access to the single market and have warned the Brexit negotiations will be tough.
The prime minister may be unwilling to give a "running commentary" on Brexit plans and negotiations, but we can be confident that the select committee will.
The pound rallied after Mrs May allowed her backbenchers to support a Labour motion calling for a full debate on the Brexit plan but the short-term boost is unlikely to continue, as she refused to commit to a vote on her Brexit strategy.
"This would not be for the goal of blocking the Brexit process, but simply to ensure that process will lead to the best possible outcome for Britain, and that the Government's proposed plan will deliver that outcome. We are not going to provide a running commentary on leaving the European Union".
"On the other hand, should the Court rule that the government can proceed alone, this could be the trigger for the next leg lower in sterling".