Chesterfield Borough Council last weekend launched a "well dressing" with a blessing service that marks the 20th anniversary of Princess Diana's death in a Paris car crash.
A well dressing involves using only natural materials, including seeds, berries, leaves and flowers to make a mural.
But the likeness in the mural has become a source of mirth online after the council posted photos on Facebook, where it has attracted derisive comments.
Mark Patrick said: "I don't know about forever in are hearts it's more like forever in our eternal nightmares after seeing this."
"It looks like biscuit. Won't it be attacked by wildlife?" Sammy La Rue asked.
Another commenter said: "At least it can double up as a Halloween decoration next month."
Louise Foyster said while it was "horrific", it was "putting Chesterfield on the map".
Derbyshire's local tourism body says well dressing is an ancient tradition in the county that died out last century before being revived in Chesterfield in 1991 as part of an exhibition about the region's traditions.
Others were angry the council publicly displayed such a poor piece of work in tribute to the much-loved Princess and mother to Princes William and Harry.
"What an insult to Dianna [sic]. Luckily she had a sense of humour and would probably be laughing if she could see it or cared. But still it needs taking down it's not nice at all," Gayla Tuckley said.
Karen Byfleet said the mural was "absolutely horrendous" and made her, "ashamed to say I come from Chesterfield".
"How much of our money has gone into this? Chesterfield Borough Council you should be ashamed of yourselves," she posted.
'Well done for the memorial to a wonderful lady'
However, the artists and their piece did receive some support.
"Considering it's made of flower petals and likely not by a professional artist it's really good. Everyone's a critic these days. Well done for the memorial to a wonderful lady," Emma Jayne said.
Richard Pearson added: "Everyone should get a life! It's a well dressing not a real-life portrait and it's a great tribute. Well done and keep up the traditions."
Some have also seen a likeness between the Chesterfield work and the "restoration" of a 102-year-old Spanish fresco of Jesus by an elderly parishioner in 2012 that was derided as a crayon sketch of a "very hairy monkey in an ill-fitting tunic".
"Bold choice from Chesterfield Council going with controversial artist Cecilia Gimenez. But I must say, it's definitely consistent with her work," Sam Tattz said.