Cameron praises 'single market' UK
The Prime Minister will hail the UK as one of the world's "oldest and most successful single markets" as he campaigns to keep the country together.
With just three weeks to go until the independence referendum, David Cameron will address the business organisation CBI Scotland's annual dinner in Glasgow this evening.
The Conservative leader will use his trip north to make the business case for Scotland remaining in the UK.
It comes the day after 130 business leaders in Scotland signed an open letter which declared that the case for leaving the UK ''has not been made''.
But Scottish First Minister Alex Salmond challenged the Prime Minister to use the visit to set out what extra powers would come to Scotland in the event of a No vote next month.
Mr Salmond said independence would give Scotland six new powers which could boost employment - overall control of Scotland's finance, control over the business tax system, responsibility for air passenger duty, as well as power over employment policy, trade policy and immigration.
The SNP leader said: "As we approach September 18, people and business leaders are waking up to the opportunities of independence.
"With full control over economic powers, we have the opportunity to tailor economic policy to our needs, which means a jobs policy that puts the interests of Scotland first."
But Mr Cameron will tell business leaders tonight that the United Kingdom is " one of the oldest and most successful single markets in the world".
He will add: " 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% of Scottish financial services' customers are in England, Wales and Northern Ireland.
"Then there's the world-famous gaming industry, cutting-edge sub-sea technology and life-saving biomedicine - all selling far more outside Scotland than inside."
The Prime Minister will attribute this success to the " skill of people in Scotland ... and the opportunities that come from being part of something bigger".
As part of the UK, he will argue, Scotland has access to a " large domestic market, 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 say that means that "o urs really is an economy of opportunity".
Mr Salmond, however, said Westminster politicians regard London and the South East of England as the UK's economic powerhouse, and as a result it is " inevitable that they will focus jobs and investment there".
The First Minister pressed Better Together leader Alistair Darling on what extra powers Scotland could get to boost job creation when the two men clashed in a TV debate earlier this week.
But the SNP leader said the former chancellor was " unable to name any job-creating powers guaranteed by a No vote" and added he was now "laying down the same challenge to the Prime Minister".
Mr Salmond said: " I have challenged David Cameron to a debate, now that Mr Darling has said he will refuse any more head-to-head encounters - but whether he accepts that challenge or not, the PM must use his visit to Scotland to say what powers Westminster is guaranteeing, to allow the job-creating businesses of Scotland to boost employment and the economy.
"If he fails to do so, the choice is clear - a Yes vote which guarantees the powers Scotland's companies and entrepreneurs need to create jobs and opportunities for future generations of Scots, or a No vote which will deliver absolutely nothing."
Tony Banks, chair of the pro-independence Business for Scotland group, said: " With independence we'll see proper support and promotion for Scottish exports and a business environment tailored to the needs of our businesses.
"We need a government that looks out for our interests rather just being obsessed with the bankers and financiers in the City of London, and we'll only get that with a Yes vote."
The Electoral Commission said it will monitor spending on the CBI dinner to ensure it does not exceed the £10,000 limit for individuals or groups who are not formally registered as campaigners in the referendum.
It follows a letter to the elections watchdog from Business for Scotland.
The Commission said it does consider the dinner a campaigning event as it includes a "high- profile speaker from one side of the referendum debate who is likely to set out their views about the referendum to a large audience".
A spokeswoman said: "We are of the view that 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 with 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've received, we're content that the CBI will not be spending more than the £10,000 limit that would require them to formally register as a campaigner at the referendum. We will continue to monitor their activities to ensure that this remains the case and we will be obtaining from the CBI the final costs of the dinner after it has been held."
The CBI caused controversy when it decided to register as a supporter of the campaign for a vote against Scottish independence earlier this year.
Some members quit in protest and t he CBI later dropped the plan.