The British Library, once denounced by Prince Charles as a building suiting an academy for secret policemen, has been awarded the highest heritage honour, Grade I-listed building status.

The institution, on Euston Road, London, now a victim of its own success with scholars and researchers complaining of students and tourists crowding the reading rooms and cafes, was opened by the Queen in June 1998 – more than 20 years after it was first approved and at £350m over the original budget, to a chorus of contempt.

Roly Keating, chief executive of the library, warmly welcomed the honour for the UK’s largest, most expensive, and arguably most controversial public building of the 20th century.

“We are delighted that Colin St John Wilson’s courageous and visionary design for the British Library’s London building has been recognised by a listing at the highest level. Even in the relatively short period since its opening it has worked its way into the affections of millions of visitors and researchers, who have discovered its beautiful spaces, subtle use of natural light and exquisite detailing.”

Roger Bowdler, Historic England’s director of ­listing, described the library as one of England’s finest modern buildings. He said the listing was in recognition of the building’s outstanding architectural and historic interest. “Colin St John Wilson’s stately yet accessible design incorporates fine materials and a generous display of public art,” he said. “The library’s ­dramatic and carefully considered interiors achieve its ultimate goal: of creating a space to inspire thought and learning.”

The heritage minister, Tracey Crouch, said: “The British Library divided opinion from the moment its design was revealed, but I am glad that expert advice now allows me to list it, ensuring that its design is protected for future generations to enjoy.”

Wilson, the architect, who was noted for his commitment to public buildings, died in 2007 bruised by the decades of controversy over the building, never knowing his creation would become one of the newest buildings ever to be awarded Grade-I status, an honour shared with the Lloyd’s building in the City, and the former Western Morning News building in Plymouth.

The library contains original works of an array of literary artists, including James Joyce. Photograph: Getty Images

He was eventually awarded a knighthood, but the controversy almost broke his heart, and destroyed his business: he described it as his Thirty Years War, from his first involvement with a proposal in the 1960s to expand the Bloomsbury museum site to hold the library, and from 1974 on to build on a derelict goods yard at St Pancras.

The history of the building, delayed by serial political meddling, was infamous. In 1988, with building already started, the Conservative government slashed the size of the project. The completed startlingly red-brick library, with its huge courtyard filled with sculptures, was denounced as an eyesore and scandalous waste of money by politicians and members of the public. It was dubbed, by a parliamentary committee, “one of the ugliest buildings in the world”.

The British Library was originally part of the British Museum, but by act of parliament became a separate institution on 1 July 1973. Part of the vitriol came from readers who could not forgive eviction from the beautiful round Reading Room in Bloomsbury – now the centrepiece of the museum’s Great Court – where famous predecessors included George Bernard Shaw and Karl Marx.

The British Library extends deep underground to hold an ever expanding collection, around 150m objects growing by an extra 1.5m items a year. The oldest texts In the collection long predate books, inscribed into 3,000-year-old Chinese oracle bones, with other treasures including Shakespeare’s First Folio, a Gutenberg bible and the originals of literary classics including works by Jane Austen and James Joyce.

The library also has a huge and growing sound archive, including recordings of Nelson Mandela’s trial speech, and the crackly voice of Alfred Lord Tennyson reading The Charge of the Light Brigade.

The library is being listed along with seven post-war regional libraries given Grade II status. Keating said the listings were a reminder in a digital age of “the vital importance of libraries as physical spaces of the highest quality at the heart of their commitments”.

The listed regional libraries are the Suffolk record office, built 1963-5, designed by Donald McMorran; Bebington central library, Wirral, 1967-71, by Paerson, Macauley and Owens; Milton Keynes central library, 1978-81, by Buckinghamshire county council architects; Chandler’s Ford library, Eastleigh, 1981-2, by the architect Colin Stansfield Smith; West Sussex library, 1965-6, by the architect F R Steele; Bourne Hall library, Epsom, 1967-70, A G Sheppard Fidler and associates; Lillington library, Leamington Spa, 1959-60, Henry Fedeski.