Labour today hits back strongly in the election battle for business support, with a pro-Union message signed by a wide range of significant corporate Scots.

The message has been backed by 150 people, including the chiefs and former bosses at Tesco, Bank of Scotland, HSBC bank, Scottish & Newcastle, Scottish Widows, ITV, Zurich, Bupa and Intelligent Finance.

It lists celebrity backing, including former Scotland rugby stars Finlay Calder and David Sole, Duncan Bannatyne of the Dragon's Den TV programme, Michelle Mone of Ultimo bra fame, and music industry managers behind Simple Minds.

Earlier this week, the SNP advertised its own list of 100 business-people supporting Nationalists at the Holyrood election. Sir Tom Farmer, Brian Souter and Sir George Mathewson were alongside representatives of small business.

Gordon Brown, the Chancellor, is at a business breakfast in Edinburgh today, using the message as a new weapon against the SNP.

While assembled by the Labour Party and including many senior business figures closely linked to Mr Brown, today's statement does not endorse Labour. At previous elections, Labour has been able to gather significant business support, but its attempt to get business leaders to sign up to a draft letter this month has been abandoned.

This campaign tactic, with the newspaper advert funded by John Milligan, founder of Atlantic Power, could benefit Liberal Democrats and Conservatives, and underlines Labour's dominant concern with attacking the SNP, ensuring it does not attract the many undecided voters in the vital closing week of the campaign. Earlier this week, a group of senior figures in football also backed the pro-Union message, but not Labour, in tabloid advertisements.

Labour chose not to target today's advert at readers of The Herald. The statement in it reads: "We believe Scotland's best future for investment, jobs and prosperity is being part of Britain and we believe the break-up of Britain would damage Scotland."

Among the signatories are; George Mitchell and Sir Peter Burt, both former Bank of Scotland governors; Sir William Purves, former chairman of HSBC; Peter Balfour, former vice-chairman of the Royal Bank and former boss of Scottish & Newcastle; Mike Ross, former chief executive of Scottish Widows; Charles Allen, former chief executive of ITV; Lord Sandy Leitch, former chief executive, Zurich; Brian Dempsey, a major Labour funder who last week voiced strong praise for Alex Salmond; Peter Jacobs, former chief executive of Bupa; David Murray, chairman of Rangers and Murray International Metals; Jim Spowart, founder of Standard Life Bank and Intelligent Finance; Maitland Mackie, the Liberal Democrat boss of his family's farm and ice-cream business; and Murdoch MacLennan, chief executive of Telegraph newspapers.

Sir Alan Langlands, principal of Dundee University, also signed the message, stressing it was in a personal capacity.

An SNP spokesman responded last night: "Labour can't get anyone in the business community to sign up to a Labour Party advert, and that speaks volumes. They're reduced to a front organisation."

The LibDems have not produced a list of corporate backers, but a spokesman said the party is determined to support Scottish business with more powers at Holyrood but without constitutional upheaval and uncertainty.

Elsewhere, Westminster's influential Treasury Committee handed Labour more ammunition against the SNP by raising further question-marks about the Nationalists' planned key source of revenue - North Sea oil - saying its "volatilityconstitutes a risk to taxation revenue in the future".