Council bosses have admitted that work to give one of Norwich's most historic buildings has over-run - and that the entire Guildhall clock tower has had to be removed.

Norwich City Council committed �130,000 towards the revamp of the Victorian clock tower on the 15th century listed Guildhall last summer, after the iconic building had been covered in scaffolding since 2009.

The work was due to be completed last November, but council bosses have said it is now unlikely to be finished until the early summer, because the task has turned out to be more complicated than originally thought.

And it has emerged that, beneath the massive awnings, every single stone in the Guildhall's clock tower has had to be removed - piece by piece.

It will be months before the tower, with its Victorian clock, is pieced back together and the scaffolding which surrounds it removed.

The bill to the council has also increased - to �200,000 - but council leaders said it was important the work was done properly to safeguard it for future generations.

Alan Waters, cabinet member for resources, performance and shared services at Norwich City Council, said: 'The works to the Guildhall clock tower are more extensive than originally anticipated.

'The whole of the tower has had to be removed, stone by stone, due to expanding metal contained within the joints.

'All stone removal and proposals for rebuilding have had to be agreed with English Heritage as the work has progressed.

'Currently some of the damaged stonework is being repaired in the stonemason's yard. Once repairs are complete then works will commence to rebuild the tower using as much original stone as possible.'

He said the hope was that the work would be completed at the end of May this year, but added: 'Given the uncertainties involved with this type of work, it is possible that this date may need to be revised.'

The issue of the progress of work was raised at a meeting of the city council this week, when Graeme Gee, Green councillor for Mancroft ward, questioned why the signs on the scaffolding still said the project was due to be finished by November.

A council spokesman said the signs would be changed.

Civic watchdog the Norwich Society raised concerns in autumn 2009 that the Guildhall, which is the largest medieval civic building outside of London, was being neglected.

But Victoria Manthorpe, from The Norwich Society, said the organisation was content with the work now being done.

She said: 'There was a bit more structural work to be done than was expected.

'When you get into work on buildings like this you often find there is more work to be done than you'd initially think. 'They are doing it very thoroughly and we are are pleased that they are doing such a good job.'