THE United Kingdom creates an "economy of opportunity" that independence could not match because it involves being part of something bigger that has helped support one million Scottish jobs, David Cameron will tell business leaders tonight.
The Prime Minister, in what is expected to be the first of several visits to Scotland in the final run-in to polling day, will, in a 'big is best' speech at the annual CBI Scotland dinner in Glasgow, praise the skill of the Scottish people for helping to create one of the oldest and most successful single markets in the world.
He will also highlight the advantages of the UK's large domestic market by stressing it is underpinned by a "common currency, common taxes, common rules and regulations … with no borders, no transaction costs, no restrictions on the flow of goods, investment or people".
He will declare: "Ours really is an economy of opportunity."
Some within the No camp are wary about Mr Cameron's involvement in the campaign, believing him as Tory leader to be "toxic" to the Unionist cause north of the Border. But the Prime Minister, who has described himself as "a Unionist head, heart and soul", has promised to fight to keep Scotland in the UK with "every fibre of my being".
In a speech designed to accentuate the positive ties between Scotland and the rest of the UK, he is expected to say: "This is one of the oldest and most successful single markets in the world.
"Scotland does twice as much trade with the rest of the UK than with the rest of the world put together; trade that helps to support one million Scottish jobs.
"For some industries, the proportion of trade with the rest of the UK is even higher; 90 per cent of Scottish financial services' customers are in England, Wales and Northern Ireland."
Earlier this year, CBI Scotland sparked controversy when it registered as a No campaigning body with the Electoral Commission. But after a row broke out, with some of its members resigning their membership, its registration was nullified.
Mr Cameron's visit has sparked further controversy, with a call for the Electoral Commission to investigate.
Tony Banks, for the pro-independence group Business For Scotland, said: "I would have thought the CBI had learned its lesson. Business is interested in hearing different views, but it expects bodies that claim to be neutral to provide a balanced platform involving both sides."
Mr Banks, who is chairman of the Balhousie Care Group, said if the CBI still wanted to claim it was neutral and avoid breaking the rules, it should "invite the First Minister to take part in a debate with the Prime Minister at its annual dinner ... otherwise, it once again risks breaking the law and losing what members it still has left in Scotland".
But in a swift response, the elections watchdog judged CBI Scotland had not broken campaign rules.
A spokesman said: "The CBI's dinner does constitute campaigning and, as a result, we have sought detailed assurances from them and their suppliers about the cost of this event, including comparison to previous years.
"We have also considered evidence from other suppliers about similar events to inform our view.
"As a result of the information we have received, we are content the CBI will not be spending more than the £10,000 limit that would require it to formally register as a campaigner at the referendum."