Moves to shift Norfolk's museums out of direct public control were causing deep concern last night, amid claims that councillors and the public are being kept in the dark over the true extent of the plans.

Norfolk County Council wants to look at whether the county's museums can be run by a specially created trust instead of the current arrangement of county and district council control.

Supporters believe the move could help protect the service at a time of public spending cuts by allowing it to look for new sources of funding not currently available under the existing set-up.

But critics fear the service is being taken away from the public and there will be no accountability over how the service is run and issues such as charging.

And in a joint letter, George Nobbs, Labour group leader at Norfolk County Council, David Bradford, chairman of the Norwich area museum's committee, and Rory Quinn, an executive member of the Friends of Norfolk Museums, have suggested the plans are more advanced than is being admitted to in public, accusing County Hall of taking away the museums by stealth and keeping councillors in the dark about the true state of the plans.

The letter claims the service has already appointed a 'trusts' officer, amid speculation that the trust could be run remotely from out of the county including either from Ipswich or Colchester.

But the suggestion was instantly dismissed by the county council, which insisted that talks were at an early stage and no decisions had been taken.

County Hall said officers were still in the process of drawing up the evidence to support the case for shifting to a trust model, and proposals would be presented to the ruling cabinet in July, after which a full public consultation was likely.

James Carswell, cabinet member for cultural services, said there was no hidden agenda.

'We were quite open in our Big Conversation that we were looking at ways of protecting our museums,' Mr Carswell said. 'During the Big Conversation myself and Vanessa Trevelyan (head of the museums service) went out to all the district councils to explain to them and engage with them about the idea of trust status.

'We are not doing this in the background. We are starting a process, looking at ideas while times are financially hard, we want to start looking at ways of protecting our key services like we have done with our libraries.

He added: ''We are not talking about removing a service, we are talking about setting up a trust which will safeguard the museums service. Areas which already have trust status have been able to tap into more grant funding. That could be mean we could create a money pot in the future which could help maintain the service.

'With times getting harder and with the potential of more cuts next year we are looking to the future now, rather than leaving it too late.'

Mr Carswell said he was also disappointed that the Labour leader had not raised the issue directly with him or the council's officers.

'George Nobbs is making out that we have already made the decision, but we have not,' he added. We have started the first step of engaging with the district councils. He is adding two and two and coming up with 48.'

But Mr Nobbs, who has also submitted a freedom of information request asking for details of the plans and whether there had been an attempt to keep them secret, said last night that he had been made aware of deep-rooted unhappiness among staff about what was going on within the service.

'We are being told that it's a fait accompli and it's all been sewn up, but people have been sworn to secrecy and councillors haven't had an opportunity to discuss it,' he said.

The letter warned of the deep concern about moves 'behind the scenes, to hand over our greatly prized local public museums in Norfolk to an autonomous trust.'

'In short, someone is trying to take our museums away,' the letter said. 'The buildings that house the museums...are much-loved structures that are a vital part of the history and heritage of their communities. They belong to their local councils and, through them, to the local citizens.

'They were never intended to be the preserve of a self-selecting elite body sitting as trustees and answerable to no-one very much - apart from themselves.'

The letter also claims that the council's finance staff had looked at the trust status option and 'found no financial advantages in it at all'.

Vanessa Trevelyan, head of Norfolk Museums Service, said: 'This is not being done in secret. We have had discussions with all the district councils several months ago and they said it looks as if trust status might be a constructive way forward. But we want to see what the evidence is, and that's what we are currently doing.'

She said any proposal would be governed by strict 'service level agreements' between the councils and the trust would have a fully accountable board and with board members who were either elected or appointed and comprised of people locally.

'We are not looking at giving away ownership of the buildings or the collections - they will always belong to the local authorities,' she added. 'What we are looking at is a managing trust that would manage the heritage asset on behalf of the local authorities.'