Craig Anderson, senior business partner at KPMG in Scotland, said:
It is clear that the business community is still seeking to have concerns allayed as we move closer to September 18.
Our research suggests that most businesses probably do not feel sufficiently informed to make appropriate long-term plans, with any action likely to be taken only when the outcome is known.
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A man and a woman, both in their early 20s, have been arrested in Birmingham on suspicion of terrorism offences.