A Mandurah shop owner whose store was targeted by thieves twice this week says it’s not the first time he’s been left thousands of dollars out of pocket.

Jim Kidd owner Peter Hadida said his Mandurah Forum Shopping Centre shop had been robbed of more than $50,000 worth of stock in the past year.

It comes after four children stormed his store on Tuesday, grabbing item after item from clothing racks before running away.

Mr Hadida said he had managed to grab about eight jumpers from one of the shoplifters, but still lost thousands of dollars in stock.

The business owner said he had been in retail for more than 20 years and had never seen anything like the gang of four who had preyed on his store.

CCTV footage of the theft shows thieves casually strolling through the store before grabbing items off shelves.

“It's heartbreaking to see stock to that value go out the door, time after time,” Mr Hadida said.

On Thursday night, thieves struck the store again, prompting the owner to call for more security at the shopping centre.

“(We want to) see some more security put on to ensure safety of staff in here but also so we can survive as a business,” Mr Hadida said.

No one has been charged in relation to the thefts.

Mandurah Forum say they are working with local police to curb theft and anti-social behaviour.