Gateshead Council did not approve a light projection onto the Angel of the North, which a supermarket said took place on Friday night.
Morrisons said the image of a baguette and the words "I'm cheaper" appeared on the artwork.
A spokesperson said it was not approached and did not give permission for the advert, and does not approve any lighting of the structure, even floodlights. A Gateshead Council spokesman said:
"The Angel has become a much-loved and iconic symbol of Gateshead and the wider North East.
"Many goods and services have and want to be profiled alongside it, and there is a filming process in place to work with organisations to do this, although this does not include lighting the Angel in any way.
"It is disappointing this process does not appear to have been followed."
A member of the public has been in touch with ITV News Tyne Tees to say he saw a supermarket advert, which was reportedly projected onto the Angel of the North in Gateshead on Friday evening, amid speculation that the image released by the supermarket could have been faked.
Ian Tate took the photograph below (on a time-lapse). The supermarket, Morrisons, has also insisted the projection did happen, and the images are genuine.
Gateshead Council has said the supermarket advert reportedly projected onto the Angel of the North was "impossible", because the light projection would be logistically very difficult and no one appears to have seen it.
However, the supermarket involved, Morrisons, said it did go ahead, on Friday evening, and the photo they have released, below, is a genuine image.
Did you see the baguette projection? Let us know via Facebook, Twitter or by emailing firstname.lastname@example.org.
@itvtynetees Of course it wasn’t appropriate. Did they get permission? I seriously doubt it.
A supermarket has had to apologise after an outcry over its decision to project a picture of a baguette and the words "I'm cheaper" onto the Angel of the North in Gateshead.
We're sorry if you thought we got carried away with our latest marketing. We were trying to have some fun and didn't mean to offend anybody
One of the most iconic landmarks of the North East, the Angel of the North, has been used as a supermarket advert. A picture of a baguette and the words "I'm Cheaper" were projected onto the wings of the 20-metre high public artwork in Gateshead on Friday evening.
Its creator, Anthony Gormley, is said to be disappointed that the work is being used as a canvas for adverts. At the time of its completion, in 1998, he said he hoped it would bring together the North East's industrial past with an information future, and be a "focus for our hopes and fears".
A spokesman for the supermarket, Morrison's, could not confirm whether the the firm had the permission of Gateshead Council to project the image. It said it had chosen the landmark as "synonymous with the North East".
A special service was held at the Angel of the North to remember villages in the North East where all the men who fought in WWI returned safely.
Two bikers from Wales are travelling the country, visiting all 51 so-called 'thankful villages'.
After the service this morning, they travelled to Meldon in Northumberland where they presented a plaque recognising the sacrifices made by the men from the village almost 100 years ago.
The 9-day trip across the country is also raising money for the Royal British Legion.
An exhibition has opened celebrating the 15th anniversary of The Angel of The North.
The iconic Gateshead statue, designed by Anthony Gormley, was completed in February 1998.
Artwork, photographs and writing inspired by the angel - and completed by local people - have gone on display at St Mary's Heritage Centre to mark the occasion.
The exhibition ends on Sunday - watch a preview below.