The Heritage Department has been examining the options for competition for more than a year and is expected to make a statement in the next few weeks.
'We are just a little anxious that the statement may be gung-ho for contracting out,' said Library Association chief executive Ross Shimmon.
He said contracting out the library service would undermine co-operation between authorities, leading to a reduction in the number of books and facilities available.
'It is not a business. If it was there would be commercial lending libraries,' said Mr Shimmon.
The Library Association is not the only voice of opposition against CCT.
A government-commissioned report by consultants KPMG and Capital Planning warned in July last year that libraries should not be subject to competition in the way other council services have (LGC, 28 July).