The two pictures were labelled as new age-progression images supposedly compiled by experts to help the worldwide hunt for the missing youngster who would be 16 on May 12.
They show her as a fair-haired teen.
One has her smiling broadly flashing a set of perfect white teeth.
But the Instagram pictures have not been commissioned by the Metropolitan Police’s Operation Grange team which has spent eight years probing the case.
Nor have they been approved by Madeleine’s doctor parents Kate and Gerry – a step bodies which create real age progression images say is vital in creating potentially accurate depictions.
One viewer who messaged the Instagram poster questioned if they were real and suggested the girl looked like 18-year-old US The Twilight Saga movie actress Mackenzie Foy.
They asked: “Is this an official age progression?
“It doesn’t even look like her.
“She had thinner lips.
“This look like Mackenzie Foy.”
The McCanns fear the circulation of the bogus snaps could derail the search for their daughter as members of the public they hope could spot her will recall them ahead of real or officially compiled age-progression images.
The Official Find Madeleine Campaign Facebook page – which is run on behalf of the McCanns – was forced to run a statement rubbishing the pictures.
It read: “We have received questions about a new age-progression image that was circulated on Instagram.
“This image was not commissioned by nor endorsed by Gerry and Kate or Operation Grange.”
The site listed links to the family’s other official social media accounts on Pinterest and YouTube.
“Any other accounts sharing age-progression images are not from us or Operation Grange,” the statement added.
“Thank you for helping in the search for Madeleine.”
Properly compiled age-progression pictures have been instrumental in the recovery of more than 900 missing children.
Three official images of Madeleine have been released since she vanished from her family’s holiday apartment in Praia da Luz, Portugal, while her parents dined with pals in a neaby tapas bar nine days before her fourth birthday in 2007.
In 2009 the McCanns unveiled a picture showing how she may have looked aged six which they had commissioned from the US-based National Center (corr) for Exploited and Missing Children.
The couple, from Rothley, Leics, showed it for the first time during a TV interview with US chat show host Oprah Winfrey.
It showed their daughter wearing a blue dress with a white lace collar sporting straight blonde hair with a fringe – similar to the style she had when she vanished.
Britain’s Child Exploitation And Online Protection Command produced new images the following year when Madeleine would have been seven.
They also showed how she may have looked if she was being raised in a warmer climate.
In 2012 the Met commissioned another age-progressed image of what she may have looked like at nine.
At the time Kate said she `sees Madeleine in the image’ and also her year-younger siblings Sean and Amelie.
No new images have been released since.
A family friend said though the McCanns would be keen to `get an accurate new picture out there’ they `wouldn’t do anything without consulting Scotland Yard’ which has spent £12m of taxpayers’ cash searching for their daughter.
“They are extremely grateful for everything the Met is doing to help look for Madeleine and have every confidence in the police,” the pal said.
“It would be for the force to decide if the time was right to release a new age-progression picture.
“They are in charge of the investigation.
“What no-one wants are half-cocked photos everywhere knocked up by anyone messing about on picture-editing software.
“Putting out the wrong image could do so much harm in that people may remember it instead of a true likeness.
“Even if intentions are sound it is the wrong thing to do.”
The McCanns were unavailable for comment today.
They are steeling themselves for the forthcoming 12th anniversary of their daughter’s disappearance on May 3.
A Met Police spokesman declined to comment on the new photos though a source said they were looking into them.