GLASGOW is on a ''knife-edge'' and could sink back into the dark days of economic decline unless it switches its emphasis from fighting poverty to attracting more entrepreneurs, a global expert on cities and their development warned.

Professor Edward Glaeser, an economist at Harvard University, said the city had done ''a remarkable job'' of restructuring its economy over the past few decades.

However, he cautioned: ''Despite claims of a Glasgow renaissance, economic data suggests that its rebirth is far from complete.

''It doesn't seem clear to me whether Glasgow is ultimately going to follow the pattern of Detroit, which has experienced unrelenting decline, or Boston, which has had a complete turnaround.''

Professor Glaeser, who will deliver the latest in the Allander series of lectures on Scotland's economic future in Glasgow tonight, said the success of the city, and to a lesser extent Edinburgh, depended on their ability to address a series of challenges that were facing all of the world's major cities.

These include attracting new firms and entrepreneurs; taking care of the socially isolated, including poorer residents; allowing for more affordable new housing; and facing up to transport problems relating to the inevitable increase in the use of cars.

Professor Glaeser, who has published countless critically- acclaimed books on urban development and is renowned for his research on cities, said the history of urban Scotland had mainly been dominated by the ''inevitable decline'' of Glasgow, which once was recognised as the Second City of the British Empire and boasted a population of 1.1 million.

He said every city in the US that fitted Glasgow's description as a manufacturing centre, located in a cold, Atlantic port - including Baltimore, Boston, New Haven, and Philadelphia - all declined with their populations falling dramatically as transportation cost factors diminished strikingly, companies left and productivity fell.

The great social problems of Scotland's urban corridor were in many ways the residue of the manufacturing exodus that resulted in concentrations of poverty and social distress where tens of thousands depended on government benefits, he said.

However, he insisted that Scotland's urban centre remained ''ultimately resilient'' and today was ''impressively productive'', due mainly to Edinburgh evolving from being a court town to a banking centre thriving in the information age.

''Edinburgh's universities and its remarkable beauty serve to attract the skilled who, in turn, provide the basis for urban success.

''Indeed, just as Glasgow's decline between 1960 and 2000 seems unavoidable, Edinburgh fits the pattern of urban success.''

Professor Glaeser said Glasgow had done ''a remarkably good job'' of restructuring its economy over the past few decades but was still almost completely a ''service economy'' with a much lower skill base than Edinburgh.

''At present Glasgow is proving to be more like Boston, which has successfully transformed itself from a being manufacturing town to a capital of the information age,'' he said.

''However, Glasgow remains on a knife-edge between sinking back into the world of just another declining city like Detroit, or becoming the bright future of an Atlantic, intellectual city.

''Glasgow still has huge economic inactivity rates.

''Huge areas of the city, particularly the inner ring around its core, is mired in poverty.''

Professor Glaeser added: ''The current policies seem good - continuing to move in a direction that is friendly to high-skilled workers and towards entrepreneurship.

''Heading in a particularly schools-orientated direction is a way of working against inner-city poverty.

''However, if you went the other way round and erected huge regulatory growth barriers, stymied the growth of car-orientated areas on the edge of town, and raise taxes for skilled workers, one could easily imagine things spiralling in the wrong direction.''

He said he favoured a very active government that helped the least disadvantaged.

But he added: ''The focus should be more on strategies that can potentially help the younger generation to avoid being mired in poverty. This requires the quality of schools to be improved, a safe environment for children to grow up in which is critical in attracting highly skilled people, and an aggressive change in housing policy. It is critical that the government helps.

''There must be a regulatory system that is friendly to entrepreneurship and friendly to new housing construction,'' he added.

Jeremy Peat, group chief economist with the Royal Bank of Scotland, said he shared Professor Glaeser's view that Glasgow had made major strides over the past four or five decades.

He said: ''The changes have been dramatic and for the better but the job is certainly not complete and never will be complete.

''We are in a rapidly-changing, globalised environment and continued movement up the productivity and skills ladders has to be made all the time.''

Charles Gordon, leader of Glasgow City Council, declined to comment last night.

However, a council spokesman said: ''We are committed to tackling poverty through economic growth. The two are linked.

''Glasgow has benefited from just under 70,000 jobs being created in the past six years and about (pounds) 2m of property development comes into the city each year.''