The Cannes Film Festival has come under fire after reports that women were turned away from a screening for wearing flat shoes instead of heels.

The women - some of whom were said to be older with medical conditions - were attending the world premiere of Cate Blanchett's new film Carol.

Screen Daily said the festival had confirmed heels were obligatory for women at red carpet screenings.

However the director of the festival said the "rumours" were "unfounded".

Thierry Fremaux tweeted: "For the stairs, the regulations have not changed: 'No smoking, formal wear'. There is no mention of heels."

A note about dress codes on the festival's website appears to reinforce his point. It says "black tie /evening dress is required for gala screenings" - with no guidance on heel height.

Screen Daily first reported the story, after a "Cannes regular" told them how a woman wearing Rhinestone encrusted flat shoes was denied entry.

The unnamed source said: "Someone I know was turned away for wearing nice flats, nothing you would wear to the beach. They were in their 50s. They told her she could go and buy appropriate shoes and come back."

Asif Kapadia, whose Amy Winehouse documentary screened at the festival last weekend, also tweeted that his wife had been challenged over wearing flat shoes, although she was eventually allowed in.

The story provoked widespread outrage on Twitter, where the head of film at the SXSW festival, Janet Pierson, tweeted a link to the story with the words: "Why I don't go to Cannes".

British writer Caitlin Moran tweeted: "Utterly extraordinary it's reported that women - including those with disabilities - are being TURNED AWAY at Cannes for not wearing heels."

Buzzfeed's film critic Alison Willmore said actress Emily Blunt had been asked about the story at a press conference while promoting her own film, Sicario, at Cannes.

"I think everyone should wear flats," the Devil Wears Prada star said, Willmore reported.

Todd Haynes' film Carol, which is screening in competition, stars Blanchett and Rooney Mara and is about an illicit lesbian romance in 1950s New York.

The women were apparently turned away from the premiere of Cate Blanchett's new film Carol. Photo: Reuters

The festival said it had made efforts to address the gender imbalance between male and female directors this year, despite only two female directors being in competition.

They selected French director Emmanuelle Bercot's drama La Tete Haute (Standing Tall) to open the festival and organisers hosted a UN conference into equality on the red carpet.

Director Agnes Varda, who made her name during the French New Wave of the 1960s, will also become the first woman to receive an honorary Palme d'Or.

The Times arts correspondent Jack Malvern tweeted: "So much for the year of women."

Irish Times journalist Laura Slattery tweeted: "But Cannes, flat shoes are in fashion this year... Well, they definitely are now."