Historian Guy Walters has written to the Culture Secretary as users continue to complain about access restrictions at The National Archives (TNA).
TNA reopened in July following the coronavirus lockdown, with new restrictions.
The building is only open to the public on Tuesdays to Fridays, 10am-2.50pm.
All appointments are pre-booked and visitors can consult a maximum of nine documents, which must be ordered in advance.
In his letter to Oliver Dowden, the Secretary for Digital, Culture, Media and Sport, which he posted on Twitter, Walters warned: “There is no doubt in the mind of any historian working in this country today that TNA has become a shadow of its former glory, and is no longer fit for purpose.
“In essence, the archive is closed.”
Other visitors to TNA have complained about difficulty accessing the facility.
Who Do You Think You Are? Magazine reader David Matthew said: “I tried to book a seat for two weeks’ time and there were no seats available by 10.12 am, just 12 minutes after booking opened.”
Walters, a novelist and historian, told WDYTYA? Magazine he was concerned that coronavirus precautions were “the Trojan horse through which restrictions will come in and never leave us”.
In March 2020, TNA announced a six-month trial of a new document ordering system that would limit visitors to 24 documents per day.
The trial was delayed when TNA closed under lockdown.
Walters said: “This kind of creep of restrictions has been coming in, and it’s been making The National Archives more of a place that’s beneficial for the people who work there rather than for the benefit of the people who need to use it and the people who pay for it, the taxpayer.
“It should be there as an archive to preserve and to let people consult documents.
“At the moment it seems to be that the storing and the maintenance of documents is almost more important than them being looked at.
“There is no point in preserving a document that no one is ever going to look at, a document that you keep hidden.
“It is better for a document to be looked at a thousand times and destroyed than a document to be preserved and never looked at.
“Be they family historians, academic historians or type of historians, the users should be the priority for the archive.”
He said that the nine document limit “totally militates against the idea of any decent historical research”, because historians can’t know in advance whether they’ll need a document for seconds or for hours.
A spokesperson for The National Archives said: “We are an organisation with a strong record of customer service and satisfaction over many years.
“However we recognise the very real disappointment and frustration these restrictions cause for both new and regular users.
“We are committed to giving the best access to the public record that circumstances allow and will continue to remodel our services to meet user demand wherever possible.”