The independence referendum is "undoubtedly causing some uncertainty" for investors, a top UK-wide company has said.
Breedon Aggregates, which employs around 580 of its 1,000 staff in Scotland, reported strong performances in both England and Scotland in its annual results 2013.
But it said the independence referendum "could be delaying investment decisions", and it is not seeing the same improvement in transport, energy and infrastructure in Scotland as in England because "government expenditure has not been increased".
Executive chairman Peter Tom said its overall markets "at last showed encouraging signs of life in 2013", and the outlook for 2014 "is more encouraging than for some time".
"We have genuine reasons to be optimistic about the prospects for 2014 and 2015," the company report said.
"The outlook in England appears to be somewhat better than in Scotland, particularly in the East and West Midlands where manufacturing investment is increasing, supported by local government investment and a buoyant housing market.
"In Scotland, there are several large projects on the horizon, including the Aberdeen relief road which is currently out for tender and should start towards the end of 2014.
"However, Government expenditure has not been increased and therefore we are not seeing the same improvement in transport, energy and infrastructure as in England.
"The independence referendum in September is undoubtedly causing some uncertainty and could be delaying investment decisions."
Breedon, based in Monifeith, Angus, completed its two largest acquisitions to date at Marshalls' quarries in England and Aggregate Industries' operations in northern Scotland at a total cost of £54 million.
Meanwhile, Moodiesburn-based sausage manufacturer Devro, which employs around 500 people in Scotland, said the outlook for its UK market is "less clear" than its other emerging markets, citing the strength of sterling and record pork prices as particular challenges.
Last week, pro-UK businesses warned that the annual results season would see more warnings of "uncertainty" as the independence referendum approaches, but pro-independence businesses dismissed these concerns as "scaremongering" and "excuses".
A Scottish Government spokeswoman said: "Businesses are continuing to invest heavily in Scotland in the run-up to the referendum, as statistics show.
"The recent Ernst & Young Attractiveness Survey also showed Scotland to be the most attractive destination within the UK after London and the South East for inward investment.
"However, it is only with the full powers of independence that we will be able to properly use all the economic levers other countries in Europe take for granted and grow the working population, increase productivity, boost exports and innovation and reindustrialise Scotland's economy."#
A Better Together spokesman said: "As last week's intervention from Standard Life made abundantly clear, leaving the UK would cost jobs here in Scotland.
"Alex Salmond's failure to tell us what will replace the pound means companies like Standard Life, RBS and now Breedon Aggregates, which together employ thousands of people in Scotland, have warned about the big risks involved in going it alone.
"As part of the UK we have the strength and security of the pound, which supports jobs and keeps costs down for families. There is no sense in putting that at risk."