A security camera captured a man stuffing an entire rump under his jacket before trying to leave Whanganui's Mad Butcher shop and being thwarted by a staff member.

The footage showed the man attempting to walk off with the 6.8kg $123 rump, but being blocked by the female employee who had been working nearby.

The video was posted to the Mad Butcher Wanganui Facebook page on Tuesday and within four hours it had more than 6000 views and 100 comments.

Dave Tighe, owner/operator of the Mad Butcher on Victoria Ave, said he also had close-up images of the man, but did not intend to post them.

"I just posted the video for awareness that, if you're coming into my shop, beware of my cameras because I've got really good ones," Tighe said.

"People want me to name and shame, but I don't want to do that. That's not me. I don't want to hang him over it, he probably needs the meat."

When the man entered the store on Monday, the employee began waving and calling out to staff members in the butchery when she realised what was going on.

However, they were all hard at work and the mincer was operating, meaning it was too loud for any of them to hear her.

Tighe said the experienced employee was a little bit shaken after the incident and that her adrenaline probably took over.

"She was worried about losing the meat and didn't really care about herself to be fair," he said.

"I told her like 'he could have took a knife out and stabbed ya, don't ever do that again', although I was proud and I gave her a little reward for doing it."

Tighe gathered his staff on Tuesday morning to discuss what had happened and to remind them about their procedures in the event of suspicious behaviour.

The procedure is that if someone enters the store looking suspicious, checkout staff are required to ring a bell that will send out a staff member from the back.

Tighe said suspicious customers could be people who are constantly looking around or those who enter the store on a warm day wearing a large jacket.

"Normally I'd go over to them and start chatting to them. I'd ask them if they were okay and I'd walk around the counter talking with them," Tighe said.

"Those are the procedures I've been doing for years and that way they don't get out because you're right there."

Tighe came to New Zealand from Dublin 15 years ago and started working at the Mad Butcher in Auckland before moving to Whanganui five years ago.

He has witnessed a couple hiding products with their baby in a pram and a man who tried carrying $400 worth of prime rump in a trench coat from one of his stores.

"That fella yesterday was pretty brazen. The girl was right beside him and she was watching him and he still done it. How stupid is that?

"If he actually said to me 'Dave, mate, I need a bit of meat', I probably would have given him pre-cooked sausages for nothing rather than rump steaks."