By Elizabeth Piper
LONDON (Reuters) - British Prime Minister Theresa May said on Wednesday parliament would have every opportunity to debate her government's plans to leave the European Union, but ruled out letting it vote on triggering the formal Brexit procedure.
May has been under pressure to divulge more of her plans for Britain's exit from the bloc beyond her catchphrase that "Brexit means Brexit", but in a lively session of parliament her government said it had little concrete to give away.
Uncertainty over what kind of deal Britain will pursue in some of the most complex talks it has undertaken since World War Two has unsettled investors and markets.
The British currency is particularly sensitive to any suggestion that the country might be heading toward a "hard Brexit", or a clean break from the EU's single market of 500 million consumers in order to control immigration.
Sterling, which has lost 18 percent against the dollar since the June Brexit referendum, rallied on reports that parliament would get to vote on May's deal, but eased slightly after her spokeswoman said there would be no vote on triggering Article 50 of the EU's Lisbon Treaty. This starts the formal negotiation process, lasting up to two years, until Britain's departure.
"The idea that parliament somehow wasn't going to be able to discuss, debate, question ... was frankly completely wrong," May said when asked by an opposition Labour lawmaker whether parliament would get a vote on the government's Brexit plan.
"Parliament is going to have every opportunity to debate this issue."
Increasingly conscious that markets are moving on her words, May was clear that she would be "ambitious" in talks with the other 27 EU members to get what she called the best deal.
"And that will include the maximum possible access to the European market for firms to trade with and operate within," May told parliament, a statement which helped sterling gain around a quarter of a cent against the dollar.
Appointed prime minister shortly after the June 23 vote on EU membership, replacing David Cameron who resigned, May has come under pressure to drop her insistence that she will not give a "running commentary" on the Brexit negotiations.
By refusing to debate her strategy, lawmakers say, May is undermining Britain's centuries-old parliamentary democracy. May says she does not want to show her hand before the talks.
"How are you going to build a consensus around your approach if you won't tell this house what your approach is?" Labour Brexit spokesman Keir Starmer said. "The mandate on the 23rd of June was not a mandate on the terms (of a Brexit deal)."
Labour demanded Wednesday's debate and May accepted on condition that it would not undermine her negotiating strategy.
May, a former interior minister, has defended her "prerogative" to trigger the departure without parliamentary approval and her government will defend that position at London's High Court on Thursday, when a legal challenge led by a pro-EU investment fund manager will begin.
Investors fear that, with three leading Brexit campaigners among her closest advisers, May is taking Britain toward a "hard Brexit". On Tuesday, several senior bankers said they could start moving staff abroad as early as next year if there was no clarity on access to the single market.
Brexit minister David Davis told parliament the government was not yet in a position to provide details of what it wanted from the talks beyond its "overarching aims".
He said the talk of "soft" and "hard" Brexit should be avoided because there was "a spectrum" of options for Britain as it negotiated its exit from the bloc that it joined in 1973.
"The overarching aims are these: bringing back control of laws to parliament, bringing back control over decisions of immigration to the UK, maintaining the strong security cooperation that we have with the European Union and establishing the freest possible market in goods and services with the European Union and the rest of the world," he said.
"We have been pretty clear on the overarching aims, not the detailed aims. We’re not even at the point that that’s possible," Davis added.
(additional reporting by Kylie MacLellan, William James, Peter Hobson, editing by Peter Millership and Gareth Jones)