SCOTTISH Secretary Alistair Carmichael has welcomed comments from the leaders of England's biggest cities calling for closer ties, rather than "greater separation" from Scotland's main centres.

He spoke out after attending a meeting of the Core Cities Group, which represents Birmingham, Bristol, Leeds, Liverpool, Manchester, Newcastle, Nottingham and Sheffield, held in Glasgow yesterday.

In a letter to The Herald yesterday the leaders of the eight English city councils backed calls for more devolution of economic development powers to help them boost their local economies, arguing it was "a more radical constitutional agenda than establishing a border at Carlisle".

Mr Carmichael said: "I agree with the Core Cities Group view that the best way to help economic growth is to work together and learn from one another to our mutual benefit, no matter which part of the country you are from."

He added: "That positive future and our shared ambitions are not served by erecting the barriers, borders and burdens within our country which would be put in place by independence.

"Our cities face common challenges, from connectivity to economic development, and there is far more which unites us than divides us. Using a secure, common currency in the UK pound is a prime example of a benefit which would be lost on leaving the UK."

First Minister Alex Salmond used a speech in Carlisle on St George's Day last month to argue that independence would create new opportunities for co-operation between Scotland and the North of England.

A spokesman for the First Minister said:"The First Minister was delighted with the reception to his recent speech in Carlisle, where he described how Scotland and England would remain closest friends after independence.

"In his speech the First Minister announced a feasibility study on work on high-speed rail beginning from north to south - rather than waiting 30 years for it to be delivered by Westminster.

"After a Yes vote we will host a series of special forums on economic co-operation with the north of England.

"While the Westminster parties are content for the dominance of London and the South East to continue, an independent Scotland can become a powerful economic counterweight to the gravitational pull of London, helping rebalance growth across the British isles."