Attempts have failed to save a giant artwork threatened with demolition to make way for a £100m city centre development.
More than 2,500 signed a petition urging the mural of the 1839 Chartist uprising in Newport should be saved.
But heritage body Cadw said the artwork does not meet its "special architectural interest" criteria.
Newport council said moving the work would cost £600,000 and might not work.
The 35m (115ft) mural, a mosaic of 200,000 pieces of tile and glass, was created in a walkway off John Frost Square by artist Kenneth Budd in 1978.
It details the 1839 Newport rebellion that left up to two dozen people dead.
Chartist leader John Frost, a magistrate and mayor of Newport, was transported to Tasmania but later returned and campaigned for political reform until his death aged 93.
The artwork faced demolition in 2009 under a previous development proposal that was later scrapped.
But current plans for the Friars Walk shopping centre remain on track, prompting the 20th Century Society, a charity that champions building and public art, to call for its preservation.
It asked Cadw to consider listing the mural which it described as "beautifully executed with an incredible amount of special detailing".
But Cadw has decided it did not warrant national level protection.
It said: "The quality of the building to which the mosaic is attached is poor and the underpass itself has no intrinsic design merits.
"It was also felt that there was no specific association between the location of the mural and the Chartist uprising.
"The location of Westgate Hotel on Commercial Street, which has been listed, has a more tangible link to the uprising since it was the scene of a bloody exchange of fire between Chartists and soldiers."
Newport council said it had taken Cadw's advice to bring in engineering experts to advise about moving the artwork.
Their report found moving it would cost at least £600,000 and there were "real risks that the mural would not survive such a move".
A council spokesperson said: "It was also acknowledged that there was a danger that relocation, or leaving the mural in situ, would jeopardise the Friars Walk scheme which is seen as vital for the regeneration and revitalisation of the city centre.
"We are aware that the mural does mean a lot to some people but the council has had to consider the wider picture.
"Unfortunately, it may have proved a fruitless effort to save the mural and too big a price to pay, both financially and for the overall good of the city and its residents.
The spokesperson added said the council is to commission another memorial to the Chartists and will consult on that.