Image copyright Getty Images Image caption Spanish actress Penelope Cruz - the report says Hispanics are "underserved" and "sexualised" by Hollywood

Hollywood movies are under-representing non-white ethnic groups in the US, a new study says.

Hispanic actors played only 4.9% of speaking parts in 2013 blockbusters, despite making up more than 16% of the population.

Black actors were cast in 14.1% of roles and 17% of films had no black speaking characters.

The University of Southern California report studied almost 4,000 characters in the 100 top-grossing films of 2013.

Although 2014 saw Steve McQueen become the first black director to win an Oscar for his film 12 years A Slave, the study found that there were only 1.1% more black characters on the big screen than in 2007.

It added that if a film had a black director, more black actors were likely to be involved.

"Adding diversity to the director's chair may influence what we see on screen," the report said.

Image copyright Getty Images Image caption Steve McQueen became the first black director to win an Oscar in 2014

It said there had been no "meaningful change" - which it set at 5% - in the frequency with which any racial or ethnic group had appeared in popular films in the seven years from 2007-2013.

Hispanics were "clearly the most underserved" racial or ethnic group, the report said.

Although they were cast in only a small percentage of parts, Hispanics bought a quarter of all movie tickets in the US, and command about $1 trillion (£593m) in spending power.

Despite the changing demographics of the US population, "films still portray a homogenised picture of the world", the report said.

"In fact, nearly half of children under age five in the US are not white," it continued, "which means that both the current and future audience for films is far more diverse than what is shown on screen."

The report also found that Hispanic women were shown in "sexualised" portrayals more than any other ethnic group.

More than 37% of Hispanic female characters were shown either naked or partially naked.

The report suggested that this "illustrates how existing cultural stereotypes may still govern how characters from different backgrounds are shown on screen".