Sharon Osbourne has declared war on US network NBC over their treatment of her son, Jack.

The matriarch has quit her post on 'America's Got Talent', claiming the network discriminated against 26-year-old Jack by axing him from reality show 'Stars Earn Stripes', allegedly because of his multiple sclerosis (MS) diagnosis.

She told the New York Post newspaper: ''I just can't be fake. It's discrimination and it was badly handled. It's time to move on.''

Sharon will remains under contract to NBC but isn't worried about any possible ramifications.

She added: ''All they can do is stop me from being a judge on another network for five years.''

'Stars Earn Stripes' producer David Hurwitz has claimed Jack was never formally hired for the tough reality contest but Sharon and Jack insist The Deal was moving forward on a verbal commitment.

After he agreed to take part, 'Adrenalin Junkie' host Jack - who went public with his debilitating medical condition in June - received an email on May 18 from Chuck LaBella, the network's vice president of talent relations, confirming his participation.

However, soon after disclosing his condition, Sharon says she received an email from NBC, which read: ''We cannot move forward with Jack's participation''.

She also claims NBC offered to pay Jack - who said he would fund his own insurance policy - his full appearance fee, but they declined.

A representative for NBC said they regretted any ''misunderstanding'' which has led to Sharon leaving 'America's Got Talent'.