(Adds BAE Systems comments)
LONDON, March 20 (Reuters) - Around 40 percent of Scots planto vote for independence in this year's referendum, according toa poll on Thursday which showed a three-point rise in supportfor an end to the country's 307-year-old-union with England.
The poll, carried out by Panelbase, showed that 45 percentof those questioned intended to vote against Scottishindependence, a decline of two points from the last equivalentsurvey.
Scotland, which has a population of just over 5 million andwhose territorial waters are the source of much of the NorthSea's oil and gas, will vote on Sept. 18 on whether to leave theUK.
Fifteen percent of the respondents said they were stillundecided.
Support for Scottish independence appears to have gatheredpace over the last month, according to three different polls, asthose opposed to independence have stepped up their campaign.
Last month the British government warned that Scots couldlose the pound if they vote to leave the UK, and high-profilebusiness leaders including the bosses of oil giants BP and Shell have expressed concern about Scotland goingit alone.
Europe's biggest defence contractor BAE Systems onThursday became the latest British company to enter the debate.
"It is clear that continued union offers greater certaintyand stability for our business," BAE's chief executive Ian Kingsaid in the FTSE 100 company's annual report.
BAE, which employs 3,600 people in Scotland, called itsinterests there "significant".
"In the event that Scotland voted to become independent, wewould need to discuss the way forward with the Ministry ofDefence and UK government, and work with them to deliver thebest solution in those circumstances," King said.
BAE's activities in Scotland include building warships suchas Britain's new aircraft carrier HMS Queen Elizabeth.
For the independence poll, Panelbase surveyed 1,036 peopleover the week to Mar. 14, having last asked 1,022 people thesame question in February. The question was: "How do you intendto vote in response to the question: Should Scotland be anindependent country?"
All Scottish residents aged 16 or over can vote in thereferendum and if a majority vote in favour of the move,Scotland will become an independent country on March 24, 2016. (Reporting by Sarah Young; editing by Andrew Roche)