For centuries it has been a haven of cultural refinement, a stunningly beautiful mansion in which Chopin composed, George Sand wrote and Voltaire lived with his mistress.

But according to a group of furious Parisian luminaries, the Hôtel Lambert is facing "imminent disaster" from the modernising zeal of its new owner, a member of the Qatari royal family.

Plans to renovate the 17th-century building and fit it out with an array of modern conveniences such as lifts, air-conditioning and an underground car park have provoked the rage of architects, historians and glamorous former residents, who have gone to court in an attempt to halt them.

Armed with a petition of about 8,000 signatures from concerned citizens, lawyers for the Historic Paris association are arguing that the plans should be abandoned in the interests of national pride, and denounce the French government's move to approve the project as "illegal".

"This decision, which bears witness to an intolerable ignorance of the nature of a structure this significant … raises doubts about the ability of our country to take care of the management of its own heritage," said Jean-François Cabestan, an architect, and Pierre Housieaux, president of Historic Paris, in a letter of protest.

Ever since it was put up for sale by banking magnate Guy de Rothschild shortly before his death in 2007 and swiftly snapped up for an estimated €80m (£69m) by a brother of the Emir of Qatar, the future of the Lambert has been the subject of frenzied speculation by those who believe its history as intellectual playground is too special for it to be ignored.

Architects and politicians from the Commission for Old Paris first sounded the alarm bells in December, when news of the planned modernisation first emerged.

But those concerns were passed over in June by the government, which insists the building is in a "very bad state" and needs urgent work to save it from further decay.

Speaking in court last week, a lawyer for the Lambert's owner said the plans put forward were "exemplary".

But that view is not shared by his distinguished neighbours on the Ile St Louis. "[The works] risk ruining this exceptional architectural singularity," said the composer Henri Dutilleux, who has lived nearby for more than 50 years.

He has been joined in his protest by a string of celebrities including the comedian Guy Bedos, singer Georges Moustaki and film star Michèle Morgan, who owned an apartment in the Lambert for 20 years.

Reiterating the concerns of architects who warn that radical attempts to alter the building's existing infrastructure could prove problematic, the female star of Marcel Carné's Le Quai des Brumes accused the new owners of "snobbery".

"They should have built outside of Paris, they would have had all the space they liked. But maybe that would have been less chic, less elegant," Morgan told Prestigium magazine.

"The Ile Saint Louis is extraordinary; the Hôtel Lambert is the icing on the cake," Morgan added.

Commentators say the acquisition of the Lambert is an indication of how France's close diplomatic ties with Qatar are increasingly yielding commercial advantages. Sheikh Hamad bin Khalifa al-Thani was the first Arab head of state invited to the Elysée palace by Nicolas Sarkozy in 2007, and the two are said to enjoy a close working relationship which dates back to the president's time as interior minister.

A spokesman for the court hearing the case said a decision was not expected before next month.