On Sunday, the thieves broke into the world-famous Paris museum using a crane to smash an upstairs window, then stole French crown jewels worth an estimated 88 million euros ($A157 million) before escaping on motorbikes.
"Despite our efforts, despite our hard work every day, we were defeated," Laurence des Cars, the Louvre director, told a Senate committee.
"We did not detect the thieves' arrival early enough," she said, blaming it on the fact that there were not enough cameras outside monitoring the vicinity of the museum.
The outside security cameras do not offer full coverage of the museum's facade, she said, adding that, in particular, the window through which the thieves broke in was not monitored by CCTV.
Des Cars insisted she had repeatedly warned that the centuries-old building's security was in a dire state.
"The warnings I had been sounding came horribly true last Sunday," she said.
She added that she had handed in her resignation to Culture Minister Rachida Dati, who had refused it.
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