A report into the by Glasgow Centre for Population Health made headlines recently by providing one of the most convincing explanations yet for the 'Glasgow Effect'.

This is the puzzling discrepancy between health in Glasgow and in other comparable communities with similar poverty levels.

Social engineering by the Westminster Government was blamed in the headlines, but those headlines were misleading. Researchers behind the report dispute that interpretation as simplistic.

Yes, the GCPH report exposed policies that originated at Westminster, which involved viewing Glasgow as "declining" Glasgow and tackling industrial collapse by encouraging the population to leave for new towns such as East Kilbride and, later, Cumbernauld while paying small businesses in Glasgow to close and relocate.

But it was the Scottish Office and Glasgow and Strathclyde Councils which continued the policy, long after it had been moderated in other parts of the UK. Historic documents, now released, show that even after it became clear that the project was failing, ministers and councils continued the strategy.

For example, the families who moved out of Glasgow were the most motivated and economically active - good for the new towns, but ripping the heart out of communities across the city. Businesses did take the money to close down in Glasgow but many didn't reopen or found that relocating from their key urban markets left them unviable.

As the GCPH report quoted, Glasgow Labour MP Hugh Brown described the effects of the policy thus:"we are getting rid of some of our best tenants ... losing the capacity for leadership in the very communities that are creating the social problems." Then Scottish Secretary Willie Ross, also Labour, denied that the overspill policy was "skimming the cream of Glasgow".

But in 1971, under a Tory government, a Scottish Office minute conceded just that. The selective nature of migration from Glasgow was "destined ... to produce a seriously unbalanced population with a very high proportion of the old, the very poor and the almost unemployable." Yet calls to reverse the approach went unheeded.

Many more details of the research will be revealed in a forthcoming article in the journal Scottish Affairs, by report authors Chik Collins of University of the West of Scotland and Ian Levitt of Edinburgh University.

It includes contemporaneous quotes providing an extraordinary insight into the power of the civil service.

As the evidence mounted up that policies for Glasgow weren't working, officials debated whether ministers should brief aggressively or defensively. Glasgow's problems could be represented in medical terms, they concluded: "Cures sometimes have unwanted side effects". This briefing would be "near enough the truth ... and the explanation most easily reconciled with the good repute of those with past responsibility."

With the Scottish Office given resources and free rein to decide strategy for the west of Scotland, local MP Bruce Millan argued for encouraging the retention of the population in Glasgow. But a change of direction could hamper the development of new towns, and was also thought difficult politically. "The remote likelihood of adopting and implementing the policies required to save Glasgow points to the contrary course, i.e. not to save it," one junior minister wrote 1977, adding that this "becomes less unthinkable every day."

The legacy of this strategy included Glasgow's Miles Better, the Garden Festival, and much that shaped the modern city. But did it also leave us with the 'Glasgow Effect'?