The romance drama, which stars his former partner Charlize Theron as an international aid worker in Africa, and Javier Bardem as a doctor, was also ravaged by critics, with one reviewer, Dave Calhoun, calling it "awful" and "pompous".

Sean Penn's THE LAST FACE: awful. Pompous romance with human suffering as wallpaper. Pleads empathy with Africa. Zero real black characters.— Dave Calhoun (@davecalhoun) May 20, 2016

Melissa Silverstein, an advocate for gender equality in Hollywood who was at the premiere on Friday, confirmed the booing saying she joined in "for my first time".

"It was so bad that I laughed at [sic] loud at times," she tweeted.

I joined in the booing for my first time today for The Last Face. It was so bad that I laughed at loud at times.— Melissa Silverstein (@melsil) May 20, 2016

Another reviewer, Variety's chief critic Guy Lodge, jokingly suggested that The Last Face may have been why Theron had ended her relationship with Penn.

Adele Exarchopoulos — the best thing in THE LAST FACE, by the way — plots her exit strategy. pic.twitter.com/1ZCt6ElLSK— Guy Lodge (@GuyLodge) May 20, 2016

Is it possible Charlize Theron saw a rough cut of THE LAST FACE and *then* ended things with Sean Penn? I would.— Guy Lodge (@GuyLodge) May 20, 2016

Lodge also tweeted that he found it hard to pick a favourite scene "but the one where Theron and Bardem sexily brush their teeth at each other will stay with me."

Penn brushed aside bad reviews by critics of the humanitarian drama at a later press conference.

"I stand by the film as it is, and everyone is going to be entitled to their response," he shrugged, according to Variety.com. "I've finished the film so it's not a discussion I'd be of value to."

Theron and Penn seemed to keep their distance at the movie's photocall, almost a year on from their last appearance as a couple on the red carpet at Cannes.

The cast of The Last Face attend the film's premiere during the 69th annual Cannes Film Festival. Photo: Andreas Rentz

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The pair posed with members of the cast firmly between them, and avoided sitting near each other at the following press conference.

Charlize Theron, Javier Bardem, Adele Exarchopoulos and director Sean Penn attend the The Last Face press conference. Photo: Getty Images

The couple began dating in December 2013 and Us Weekly reported that they had become secretly engaged a year later, however the two never confirmed the reports.

The Last Face, which was funded partly by Penn, has been entered into the festival's biggest award, the Palme d'Or.

"I had almost enough to do this one the way I wanted to do it," he said in an interview in the Financial Times. "Then I had to pony up much more than I can afford to complete it."

"I've got an 'everything is riding on it' deal going to Cannes this year," he added. "I think [the movie] will disappear if it gets a poor reaction and I think that would be a terrible shame because it's very relevant now and the performances are transcendent ... I've given it all I've got."

Charlize Theron and Javier Bardem in The Last Face, directed by Sean Penn.

All may not be lost for Penn and The Last Face however. Films that have been booed at previous Cannes Film Festivals include Taxi Driver, which went on to win the Palme d'Or and snare four Oscar nominations, including Best Picture, and Quentin Tarantino's films Pulp Fiction, which also won the Palme d'Or, and Inglourious Basterds.

with WENN