The transfer of Glasgow's museums, libraries and leisure centres to a charitable trust is facing an 11th-hour legal challenge, which could at least delay its implementation.

Public-sector union Unison is using Victorian legislation on public libraries in its attempt to scupper the scheme, approved by Glasgow City Council in early February.

It is arguing the council acted outside its authority in allowing the transfer of libraries to a trust.

A petition was lodged at the Court of Session in Edinburgh yesterday seeking a judicial review and an interim interdict to delay the incorporation of the trust.

Unison expects a decision on the interdict to be made today and believes it has made a valid and substantial argument that the council went beyond its powers in respect of the Public Libraries Scotland Act 1887.

The city council says it and its legal advisers continue to believe the proposals are legally water-tight and will defend the action.

The challenge comes just three days before the 2000-plus cultural and leisure services staff transfer to the new body and two months before Culture and Sport Glasgow is expected to come formally into being.

Those driving the scheme believe the trust model will benefit the city by allowing the new body to seek resources from funders such as the lottery and to receive private donations the council currently cannot access. It would also be exempt from VAT and claw back millions in rates relief.

Senior Unison officials said they are seeking the review over concerns about the long-term financial viability of a charitable trust controlling the civic cultural, artistic and sporting amenities and collections, and the potential knock-on effect on staff terms and conditions.

They say trusts in England have not received the level of private funding expected, while at the same time local authority funding has diminished. There is also a lingering concern over pensions.

The union's case is dependent on section 21 of the 1887 act, which it interprets as preventing a local authority from handing over control of its libraries to a trust.

The issue was raised previously by officials from Culture Minister Patricia Ferguson's office, but they were given assurances it was not prohibited by the legislation.

The QC hired by the authority to explore the legal issues surrounding the trust, former solicitor-general for Scotland and leading Tory Paul Cullen, was yesterday still of that opinion.

Last night, Unison's Glasgow branch secretary Mike Kirby insisted the union had not taken the decision to seek a judicial review lightly but was confident it was in with a fighting chance.

Mr Kirby said: "Unison is confident that the democratic control of public services and the management of these services will be removed by what amounts to a tax scam."

Christopher Mason, leader of the council's LibDem group, said: "Labour have not consulted the people about this transfer and they have no democratic mandate for it."

John Mason, leader of the council's SNP group, said: "I believe the establishment of this trust is morally wrong, whatever a judge decides."

A city council spokesman said: "We will defend this action."