An initiative will be launched today to nudge policymakers away from seeing successful book lending and the encouragement of reading as the prime goals of Britain's public library service.

Instead the emphasis should shift to whether libraries help governments promote their wider health, educational and social objectives.

This should be seen as the modern "exciting challenge", 154 years after the opening of the country's first free public library, a Westminster seminar will be told.

"We should not look at libraries exclusively as free bookshops," one of the main speakers, Professor Mark Hepworth, is due to say. "More complex measures and methodologies are needed to properly capture the social benefits of library services."

Prof Hepworth heads the thinktank Local Futures Group and is visiting professor of economic geography at Birkbeck College, London.

The libraries minister, David Lammy, is expected to welcome the report.

The seminar will be attended by officials and politicians from central and local government and from agencies such as the Audit Commission, one of the library service's most vigorous critics. It has been convened by the Laser Foundation, a grant-making trust run partly by librarians.

The foundation has spent £50,000 on commissioning an independent report by the consultants PriceWaterhouseCoopers into mostly non book-based library services.

It comes at a time when libraries have been described as "a service in distress" by the Commons culture select committee because of the steep declines in their book loans and, until recently, their public use.

The committee's report in March stressed that book shelves were the bedrock of the service's future. The consultants' report examines projects in seven areas which involved a total of 18,000 adults and children in projects including IT tuition, summer reading, education and social outreach.

Tim Coates, a campaigner for book-based library reforms, said: "Commendable as these activities are, if the book borrowing decline continues, no one in government will be prepared to carry on funding the use of highly trained librarians to carry out these largely social objectives."