Bosses of Ford and BT have today ramped up their warnings over the need for clarity on Brexit, identifying early next year as the point of no return for a transition deal to be struck.
Steven Armstrong, vice president of EMEA for Ford, said although the auto firm was "the poster boy" for globalisation it may be forced to move parts of the business out of the UK without better certainty on offer.
He told the conference Ford wanted to "keep investing here in the UK" but said it was "vital we have a clear view" on the final agreement with the EU and an agreed transition in place as soon as possible.
Speaking separately Gavin Patterson, chief executive of BT Group, called on the government to have agreed a transitional arrangement by the beginning of next year, saying at that point any period "begins to deteriorate in value".
"If we don't have certainty at that point, businesses will be looking to their worst case scenarios [of a no deal]," he said, adding it was "not a political point" but rather an issue of planning.
Patterson said there was "no question" that firms were finding it more difficult to fill skills gaps since the referendum, an issue also raised by Vista Equity Partners' boss Robert F Smith.
"It all comes down to people," Smith said. He warned that the UK's "legacy" of strength in this area was in decline thanks to technology.
The warnings were raised shortly after Theresa May told businesses a Brexit transition period was "crucial" - but admitted it isn't guaranteed to happen.
Speaking at the annual CBI conference this morning, the Prime Minister said she was seeking a "full agreement" from the EU27 that a transition period will be put in place, after which the "details" could be set out.
"First of all we need to get full agreement that this is something that will happen. Then we’ll need to negotiate the details. Of course, some of those details you need to know what the end state is, what that future partnership is, because this is about practical change, moving to that future partnership.
"I was clear in Florence that I think businesses should have the comfort of knowing that they will be able to operate on the same basis as they currently can during that implementation period."
May noted that there were some areas that would only become clear once the full agreement was in place, but insisted clarity for businesses was top of her mind.
"I am determined to give businesses as much certainty as possible," she said, adding that had been "fundamental" to negotiations so far. May reiterated her view that the speech she gave in Florence had given talks new momentum, adding that she "particularly welcomed" the fact EU27 countries were now making internal preparations for the second stage.
May also addressed the ongoing sexual harassment scandal that has engulfed Westminster in the last fortnight. She told the conference she had been "deeply troubled" by the allegations, saying those working in parliament had the same right as people "working anywhere else".
But the Prime Minister dodged a question on whether she knew about any of the accusations before they had been made. Instead, she admitted that "a number" had been raised with her in private that have not - yet - made their way into the press.