The success of a gallery should not be measured by its number of visitors, the director of the National Portrait Gallery has said, as he suggests a significant drop in its figures is a price he is willing to pay for greater diversity.

Nicholas Cullinan, whose National Portrait Gallery has seen around 100,000 fewer visitors in 2018 than it did in 2017 according to a survey by The Art Newspaper, said it would be “easy” to programme blockbuster exhibitions to suit the masses.

But, he said, it was more important to fulfil its mission to “speak to different audiences” and “reach out” to new visitors by programming exhibitions featuring diverse contemporary artists.

A study by The Art Newspaper found the gallery had 1,586,451 visitors in 2018, compared with 1,703,411 in 2017.

Its statistics also showed that, for the first time in nine years, Tate Modern overtook the British Museum as the most popular UK arts institution, with 5.9 million guests making it the fifth most-visited gallery in the world thanks to major exhibitions including Picasso.