(Fixes typo in second paragraph)
* Scotland to hold breakaway vote on Sept.18
* Polls suggest Scots will reject independence
* New analysis shows independence campaign has stalled
* RBS says independence to bring costs, impact its business
* GRAPHIC on independence polls - link.reuters.com/dyw42w
By Andrew Osborn
LONDON, Aug 1 (Reuters) - The campaign for Scotland to break away from the United Kingdom has stalled just over a month before Scots decide whether to go it alone in a referendum, an analysis of the latest six opinion polls showed on Friday.
It came as one of Scotland's highest profile businesses, Royal Bank of Scotland, said a vote for independence could significantly increase its costs and have a material impact on its business.
The poll research, published 47 days before the Sept. 18 vote and before a televised debate on Tuesday between the leaders of the "Yes" and "No" campaigns, showed that the independence movement has been largely stuck in the 42-44 percent support range since March after making gains at the start of the year.
Published in Britain's The Independent newspaper, the analysis showed that if the results of the last six polls conducted in June and July were averaged out, 57 percent of Scots would reject independence and 43 percent would back breaking away. That gives the "No" campaign a lead of 14 percentage points.
"The 'Yes' campaign seems to have stalled while still significantly short of its destination," said Professor John Curtice of Strathclyde University, who conducted the analysis.
"There isn't any consistent evidence of movement towards a 'Yes' vote since March."
A "yes" vote would cast Britain into uncharted constitutional waters, trigger a prolonged period of uncertainty, and could diminish its clout on the world stage. A "No" vote would be likely to lead to more powers being devolved to Scotland, which already has control over swaths of policy.
The "Yes" campaign says Scotland, which has its own parliament but lacks tax-raising powers, would be freer, better governed and more wealthy if it went it alone.
The "No" campaign has warned that Scotland would be unable to keep the pound, that tens of thousands of jobs in the defence and financial sectors would be at risk, and that an independent Scotland could struggle to rejoin the European Union.
Royal Bank of Scotland, which has been careful not to enter the emotive political debate, said that uncertainties resulting from a "Yes" vote would be likely to significantly impact its credit ratings and "could also impact the fiscal, monetary, legal and regulatory landscape to which the group is subject". [ID: nL6N0Q71F1]
The Commonwealth Games, which are being held in the Scottish city of Glasgow, are due to end on Sunday with pollsters keen to see if the competition, which has gone smoothly, has altered Scots' views on independence.
The constituent parts of the United Kingdom - England, Scotland, Wales and Northern Ireland - all compete separately in the games as home nations, rather than as one in the Olympics. This spurs local pride.
Anxious to avoid being accused of politicising a sporting even, both the "Yes" and "No" camps swore off using the games as a platform for their respective campaigns. But the first opinion poll carried out during the event is expected to be published on Sunday.
Strathclyde University's Curtice, widely recognised as one of the leading experts on the independence debate, said the "Yes" camp made real progress last winter lifting their support above the 40 percent mark in January, a threshold it hadn't fallen below since.
But Curtice, who cautioned that some pollsters tended to throw up better results for the "Yes" camp than others, said it appeared that the pro-independence campaign had lost momentum at the end of March.
He said he calculated his "poll of polls" by excluding "don't knows" who have consistently made up a large proportion of respondents in polls, injecting an element of uncertainty into the outcome of the referendum.
Scottish First Minister Alex Salmond, the leader of the pro-independence Scottish National Party, has said the large number of undecided voters makes the referendum an open contest despite what the opinion polls say.
Some recent polls have shown Salmond is succeeding in winning over some of the "don't knows", though not at a fast enough pace to hand him victory. (Editing by Jeremy Gaunt)