Fast food giant Domino's Pizza may have super-sized its sales in the December half, driving them past the $1 billion mark amid concerns that some of the franchisees running its store network underpay staff to keep ahead of rising costs.

But its reported profit for the half fell short of market expectations, prompting investors to sell the stock and sending its share price to a 52-week low.

Domino's CEO Don Meij was in his usual energetic mood when presenting the company's expansion plans. Credit:Chris Hyde

Domino's chief executive Don Meij was forced to defend the chain's $5 pizza deal as he upgraded growth expectations for the company's full-year underlying earnings and net profit to 32.5 per cent on the back of a very strong first half.

Despite the raised profit target, Domino's share price dived by almost 16 per cent during Wednesday's trading session. They were down 13 per cent at $54.36 in mid-afternoon, the lowest price since February last year.