Dame Julie Andrews’s performance as Mary Poppins is racist, says a US academic who accuses her of ‘blacking up’ when her face is covered with soot as she dances with chimney sweeps.

The scene in which Poppins joins Dick Van Dyke’s Bert and his fellow sweeps on a rooftop for the song Step In Time is one of the best-loved moments in the 1964 Disney classic.

But writing in the New York Times under the headline ‘Mary Poppins, and a Nanny’s Shameful Flirting With Blackface,’ Professor Daniel Pollack-Pelzner attacks the scene. Not surprisingly, the film’s legions of devoted fans have reacted with disbelief.

The literature professor acknowledges that Poppins’s face is covered with soot because she has gone up the chimney with her charges, Michael and Jane Banks.

'A nanny's shame': Julie Andrews as Mary Poppins and Dick Van Dyke as Bert get covered in soot for the much-loved scene in the 1964 Disney classic

But he writes: ‘Her face gets covered with soot, but instead of wiping it off, she gamely powders her nose and cheeks and gets even blacker.’

He also links the scene to racism in the books by PL Travers, particularly in the 1943 novel Mary Poppins Opens The Door when a housemaid screams at a sweep: ‘Don’t touch me, you black heathen.’

He writes: ‘The 1964 film replays this racial panic in a farcical key. When the dark figures of the chimney sweeps Step in Time on a roof, a naval buffoon, Admiral Boom shouts, “We’re being attacked by Hottentots!” and orders his cannon to be fired at the “cheeky devils”.

‘We’re in on the joke, such as it is: These aren’t really black Africans; they’re grinning white dancers in blackface. It’s a parody of black menace; it’s even posted on a white nationalist website as evidence of the film’s racial hierarchy.’

Extraordinarily, Pollack-Pelzner has even found fault with the recently released sequel Mary Poppins Returns, starring Emily Blunt.

He said he was surprised by the song A Cover Is Not The Book because of its reference to a wealthy widow called Hyacinth Macaw, who wears ‘only a smile’ plus ‘two feathers and a leaf’.

Fans heaped scorn on Dr Pollack-Pelzner, pictured

In the original 1934 book Mary Poppins, the character is a ‘scantily clad negro lady’ who addressed the nanny in a ‘minstrel dialect.’ The racial references were removed in a 1981 revision of the book.

Fans online have reacted with fury to the professor’s views. One derided the piece as ‘a candidate for the stupidest New York Times article for some time’.

Another said: ‘Mary Poppins wasn’t flirting with black face! It was soot in their faces from being up a chimney!!!! Stop spreading racism claims on non-racist things like this.’ A third wrote: ‘Come on now, leave Mary Poppins out of this! Chimney sweeps in London DID have coal dust on their faces. Didn’t make them, or Mary for that matter, racist.’

Last night, Downton Abbey creator Julian Fellowes, who collaborated on a 2004 stage adaptation of Mary Poppins that returns to the West End later this year, said the scene when the nanny puts soot on her face is meant to be a gesture of support for the sweeps.

‘All she wants to do is join the sweeps and show them she isn’t standing apart – that she wants to belong to that group. It’s a touching scene and it displays a warm friendliness towards the sweeps.

‘One of the subtexts of the whole thing is that the sweeps are these marvellous people, which is Travers’s way of saying there is no such thing as an ordinary man and woman.’

The film remains one of the most successful ever made and picked up five Oscars, including Best Actress for Dame Julie.

The sequel, Mary Poppins Returns, which features cameos from Meryl Streep and Van Dyke, has taken £245 million worldwide.

Last night, Dr Pollack-Pelzner, who is based at Linfield College, Oregon, told The Mail on Sunday: ‘I don’t like hearing that something I loved and that something that was important to me in my childhood might be more troubling than I assumed. So I appreciate the strength of the reaction.

‘I just hope some of that energy can go to Disney as well and ask them to think a little bit more about how their new movies connect with the past.’

Dame Julie was unavailable for comment last night.