STAYING part of the UK's "true single market" is the key to Scotland's future economic success, Business Secretary Vince Cable will claim today.

Speaking in Glasgow to coincide with the launch of the UK Government's fourth in a series of papers on Scottish independence, Mr Cable will say a "Yes" vote in next year's referendum would "create barriers that would hamper trade with the rest of the UK, which is by far Scotland's most important market".

Mr Cable will note how these barriers could also damage the prospects for the rest of the UK, for which Scotland is currently the second largest market.

Stressing how Scottish exports to the rest of the UK, excluding North Sea oil and gas, totalled £46 billion in 2011, Mr Cable is due to point out how this is double the level of exports to the rest of the world and four times the level exported to the EU.

Mr Cable will also note how within the UK there are no internal barriers to the flow of goods, services, capital and people whereas trade between independent nations involves red tape, costs such as VAT as well as payment and reporting requirements.

He will set out the benefits of Scots firms retaining membership of the UK, such as a common set of business regulations; an integrated infrastructure for telecommunications, broadband, postal services and transport and a wide UK tax base that enables long-term investment in major projects.

The Business Secretary will also claim that access to the UK market and a highly skilled workforce has helped Scotland remain an attractive destination for foreign investment.

"The Union works for businesses on both sides of the Border," Mr Cable will insist. "Scotland is famous for its world-class products and enterprising spirit; the UK's truly free, integrated and growing market helps Scottish firms exploit these to the full.

"The last thing firms need is a new set of rules and regulations, new costs on exports, a smaller labour market and less reliable support for innovation and knowledge transfer."