The gaffe came as hosts Eamonn Holmes and Ruth Langsford were interviewing an animal charity as they appealed to find a home for ‘Britain’s loneliest dog.’
But as the camera panned back to show them sat on the sofas, the virtual image of the River Thames suddenly went black.
The mistake was spotted by some viewers but only for a few seconds, as the camera quickly cut to a close up of the dog perched on the carpet.
It was around a minute before the camera once again panned away, revealing the background restored to normal.
Several fans took to Twitter in shock that the background was fake, though it had been said that the river was a hologram when the show moved to its new home last year.
As one viewer pointed out that the view of the Thames was a plasma screen, another tweeted in response: ‘It’s all a con, my life is a lie.’
Another also tweeted: ‘Did anyone else notice the windows turning off?’
A third also pointed out: ‘Someone must of turned the window off on the This Morning set today oops and I thought it was a real window.’
When This Morning moved to its new home last year, Holly and Phil had joked that they were ‘taking the view with them’ as the background of the River Thames had remained the same.