Vittorio Sgarbi, the Italian undersecretary for culture has threatened to undermine the National Gallery's efforts to display a complete collection of the Masaccio altar pieces.

The National Gallery has spent two years organising the display of the scattered pieces of the Carmine altar, for what is thought to be the first time since the pieces were separated in the 16th Century.

The Capodimonte Museum in Naples and Pisa's National Museum of San Matteo, had granted permission for their loans to Britain, but Sgarbi, himself an art critic has threatened to block them in response to Britains alleged hoarding artworks.

Sgarbi has also threatened to ban other loans to the UK unless it became more generous in lending artwork to Italy.