Britain's Got Talent viewers left stunned as Dec Donnelly spanks David Walliams live on air

Britain’s Got Talent fans were shocked when presenter Dec Donnelly spanked judge David Walliams live on air.

The presenter was forced to take action during the live semi-final show when Mr Walliams threw confetti at him as he asked the judges what they thought of each act.

Mr Donnelly told Mr Williams “Stop it, I’m going to smash your face in.”

As the mischievous presenter laughed, Mr Donnelly said: “I think we should go to a commercial break and while the votes are counted and verified I’m going to take David over my knee and let’s see what happens.”

Mr Donnelly then proceeded to spank Mr Walliams on the bottom before the show went to a commercial break.

Viewers at home were left stunned and many took to social media to comment on the incident.

Matthew Corrigan said: “Did Dec actually spank David Walliams on Britain’s got talent?”

While another person said: “I just witnessed Dec spit on his hand and spank David Walliams.”

Earlier in the evening viewers were mesmerised by the Giang Brothers as they performed during Friday night’s semi-final.

Alesha Dixon and Amanda Holden were left shocked at one point as the brother walking backwards up the stairs, wondering if he would make the last step and looking on with horror as the brother wobbled as he walked backwards.

The grand final of the TV talent show is due to be aired on June 3.