The Friends of Flaxmill Maltings says it was told that Historic England would be responsible for the roles that it had had for many years and felt it had been left with no meaningful functions.
Trustees say they have been left saddened but proud of their achievements.
After many years of working in partnership with Historic England, The National Lottery Heritage Fund and Shropshire Council, the Friends of the Flaxmill Maltings has closed down as both a charity and a company.
Historic England has said the intention had been to support The Friends going ahead.
Chair, Alan Mosley, said: "The Friends are widely acknowledged as being a crucial factor in the successful National Lottery bid and went on to have a substantial role in the development of the visitor experience which has recently opened to the public. Over the years they have engaged with many thousands of people through the provision of learning, cultural, recreational and social events and activities.
"That pride is the culmination of 12 years of hard work by volunteers, trustees and our staff. In particular for the last six years we have worked in partnership with the main funders, The National Lottery Heritage Fund and owners, Historic England.
"We were the public face of the project, managing the previous Visitor Centre, running open days, exhibitions, tours, learning activities, talks, research, family activities, large and small events.
"However, as we progressed towards opening The National Lottery Heritage Fund and Historic England decided it would be their preference for a company set up by Historic England to take over the operations in the run-up to opening.
"We had to accept this on the basis that the Friends were to continue with their successful management of volunteers, providing a comprehensive activity plan and extensive community engagement. However, recently we were confounded to be told that these three crucial functions were also to be placed in the hands of Historic England.
"It has been a disappointing end to a roller coaster ride. We wish the project every success with the current visitor opportunities and the commercial and regeneration master planning initiatives which are to follow."
A Historic England spokesperson said: “Historic England is saddened by the decision. It has worked alongside and supported the Friends of the Flaxmill Maltings as a key partner throughout the restoration of Shrewsbury Flaxmill Maltings. The decision by the Friends to not continue operating is not what we wanted.
"Historic England temporarily provided more support for the operation of visitor services in early 2022 to ensure that the Friends of the Flaxmill Maltings had time to put in place the necessary plans and structures to run an operation of this complexity and profile. For operational reasons, it also became necessary for us to take on temporary management of the volunteers and the engagement plans. The intention was to support the Friends to be ready to take forward these responsibilities in the future, however, we respect their decision to close."
"We would like to thank the Friends’ Board, staff team and volunteers for their tireless work to bring Shrewsbury Flaxmill Maltings back to life over more than a decade. The Friends’ achievements in engaging people and the local community with the story of Shrewsbury Flaxmill Maltings through tours, talks and countless other activities were a vital part of the restoration of the site.
"Friends’ volunteers who wanted to continue their valuable work supporting this unique piece of local heritage are now part of the Shrewsbury Flaxmill Maltings team of volunteers. They are already welcoming visitors, sharing the rich story of this special place and supporting the running of the site as part of the visitor experience team.”