Weaving her way through hard-hatted workmen labouring to finish the €52m (£42m) transformation of the Picasso museum in Paris, Anne Baldassari seemed more excited than anxious.

Yes, the museum director admitted, the project had overrun by a spectacular three years and the budget had exploded by €22m. Standing in the cour d'honneur of the magnificent 17th-century Hôtel Salé, Baldassari, 58, peered from under a white plastic helmet through small round glasses and smiled. She seemed neither dismayed nor deterred.

The result would be worth the wait and "do justice to the extraordinary collection" of Picasso masterpieces, she told the cameras. To others, she was more direct. "I have given my life to this museum. I will open it. Full stop. End of story."

That was just over two months ago. Today, anticipation has turned to anger; art and high-minded cultural ideals apparently sullied by back-stabbing and squabbling.

After 23 years at the museum – nine of them in charge – Baldassari has gone, summarily sacked by Aurélie Filippetti, France's culture minister, after a staff rebellion and complaints of brutal management and a regime of fear.

The move has caused a damaging rift between the government and Claude Picasso, the Spanish-born painter's only living son, who supports the dismissed director and has now threatened to withhold donations, including one of his father's drawing books, to the museum.

Picasso, who is on the museum's board, described the sacking as scandalous and laid into the culture ministry for creating a "grotesque and insane situation".

"[Baldassari] is the scientific authority who has been responsible for the growth of the museum since many years, she has put on exhibitions with the collections abroad to raise €31m of the €52m needed for the [renovation] work, she has conceived the new spaces to rehang the collection better … I have already said and I say it again, I will be very wary and will consider as an impostor any curator who thinks they can take her place," he told Le Figaro.

Picasso also accused Filippetti of delaying the reopening of the museum once again. The planned July opening has been put back until September, even though the architects insist the building is ready and only needs a "good dusting".

Picasso said: "The truth is there is no positive desire to open the museum. I'm being messed about. I have the impression that France doesn't care about my father's work or me.

"If the minister is annoyed with Madame Baldassari, I'm annoyed with the minister!"

The Picasso museum, in the heart of Paris's historic Marais quarter, opened in 1985. Most of the exhibits were bequeathed to the French state by Picasso's heirs, according to the painter's wishes, on his death in 1973. His widow, Jacqueline, later gave a substantial number of works while friends offered legacies and donations.

Since 1985 more than 1,000 exhibits have been bought by the museum, which has a collection of 5,000 paintings, drawings, sculptures, photographs, ceramics, notes and archive documents. The museum also holds masterpieces from the artist's personal collection, including works by Matisse, Renoir and Cézanne.

Baldassari is renowned as a Picasso expert and has been the driving force behind the upgrading of the museum and its collections. But even friends suggest she overreached herself. The renovations, prompted by a need to improve access for the disabled and modernise the buildings, turned into something considerably more extensive – and expensive – than anyone imagined when the museum closed in 2009.

The building work finally began two years later, but Baldassari says renovations were held up by the listing of the Hôtel Salé as a historic building, and by strict health and safety regulations, including a long-forgotten and overlooked notice of non-conformation to fire regulations dating back decades.

The more kindly suggest that the director acted with passion, but was unable to delegate and that she presided over an atmosphere of general confusion, prompting the departure of four successive director generals.

Her critics were pitiless. The former director general Hervé Cassagnabère reportedly described Baldassari as paranoid and irrational with a "tenuous relationship with the truth" in a report to the culture ministry. Then, last weekend, after a report from workplace inspectors suggesting there was an unhealthy atmosphere "putting workers at risk", more than half the museum's 40 staff signed an email, published in Libération, accusing Baldassari of authoritarianism, partiality and managerial methods that had led the Picasso museum into an impasse. They insisted she had to go.

Filippetti promised a "rapid decision", and it fell like a guillotine 48-hours later. Baldassari barely had time to deny the accusations when she was summoned by Filippetti and fired.

The minister said she had suggested Baldassari carried out the hanging of the collection for the reopening, an offer that was refused.

A senior civil servant has been given the temporary job of running of the museum. The culture ministry said a new director would be appointed within 15 days, but added: "Apart from that we have nothing more to say."

Among those favourite to take over are Laurent Le Bon, director of the Centre Pompidou-Metz, Didier Ottinger, deputy at the National Museum of Modern Art, and Eric de Chassey, director of the Villa Médicis, in Rome.

Such dramatic departures of high-ranking "fonctionnaire" civil servants are rare in France with its strict procedures for removing anyone from their job, and lawyers will have been briefed long before the announcement was made official on Tuesday.

"This was done with great brutality and seems to have been executed even before the president was aware," Baldassari's lawyer, Henri Leclerc, said. "She was appointed by the president and only the president can put an end to her appointment."

Whether, in Madame Baldassari's words, this is "full stop. End of story", remains to be seen.