A chemist in Melbourne has been caught opening earlier than normal trading hours to sell baby formula to shoppers who are seen queuing out the door.

A video published by the Herald Sun shows a long line of shoppers outside the My Chemist on the corner of Elizabeth Street and Flinders Lane at around 7.30am. It is not made clear which day the video was recorded.

The customers are seen carrying large bags and attempt to shield their faces with their hands and hooded jumpers. A few of them also use their phones to record the person filming them.

The shoppers are seen lining up outside the My Chemist store in Melbourne before regular opening hours. (Herald Sun) (Supplied)

A man is seen grabbing a box of formula before it hits the shelf. (Herald Sun) (Supplied)

Inside the store a man can be seen grabbing a box of baby formula from a stock cart, with other shoppers clutching at boxes in a frenzy before the tins even reach the shelf.

The video has raised concerns that the store fuelling the "daigou" trade, which sees cheap Australian baby formula shipped overseas to China for double the price it was bought here.

A local resident who lives nearby the My Chemist store told the Herald Sun he was "disgusted" by the practice.

The "daigou" trade sees Australian baby formula shipped overseas to China for double the price it is bought here. (AAP) (Supplied)

“As a long-time local resident I am dismayed that businesses are allowing people without children to profiteer at the expense of Australian mothers that do (have children),” the man said.

According to experts in the daigou trade , brands like A2, Bellamy’s Organic and Karicare Aptamil are highly sought after.

International trade law Professor Justin Molban said the mark-up in price from Australia to China provided a profit motive.

A shop in Hornsby in Sydney last month saw baby formula fly off the shelves. (Facebook) (Supplied)

"Between purchasing it in Australia and selling it overseas between $70 and $90, you can see there's plenty of room there for arbitrage," he said.