ROME (AFP) - Italy's Prime Minister Matteo Renzi has defended the director of a Unesco World Heritage Site after unions filed an official complaint accusing the man charged with revitalising a Versailles-style palace of working too hard.

Mr Mauro Felicori, tasked in August 2015 with transforming the enormous Royal Palace of Caserta near Naples into a hot tourist destination, said on Saturday (March 5) the complaint had come as "a slap" but he was determined to carry on.

The 18th-century palace in Reggia di Caserta, which boasts 1,200 rooms including a grand theatre, has featured in several films, from the 1999 and 2002 Star Wars flicks to Mission: Impossible III and Angels & Demons.

"The trade unionists have to realise that the tide has turned. And the free ride is over!" Mr Renzi said on Facebook, after three unions wrote to Italy's culture ministry to denounce Mr Felicori for working early mornings, evenings and weekends.

Mr Renzi said that with Mr Felicori, 64, at the helm, visitor numbers in February 2016 were up 70 per cent on a year earlier, while takings were up 105 per cent.

The palace in southern Italy, inspired by the Palace of Versailles and built for the Bourbon king of Naples, was one of the largest buildings constructed in Europe in the 18th century and was designated a World Heritage Site in 1997.

Mr Felicori was one of 20 "super directors" hired last year by the culture ministry to revive Italy's top public museums, including the Uffizi gallery in Florence, Milan's Pinacoteca di Brera and Rome's Galleria Borghese.