The service at KFC Blenheim, on Grove Road, is causing disgruntled customers to blow off steam on social media.

Not so fast food, a closed drive-thru and wrong orders have seen KFC Blenheim come under fire from hangry customers.

The Grove Rd store has been slammed by disgruntled diners in recent weeks, with one woman claiming it "must be the worst in New Zealand".

The company that operates KFC's franchises in New Zealand has blamed the problems on a lack of staff.

DEREK FLYNN/FAIRFAX NZ A sign on the doors of KFC Blenheim on Thursday notifying customers the front counter is closed "due to our staffing situation".

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A spokeswoman for Restaurant Brands said the company was "aware of the issues" at KFC Blenheim and was looking for new staff.

"When there is insufficient staff for a shift they cannot operate the store effectively and need to close," she said.

FAIRFAX Staff shortages have previously closed the drive-thru at KFC Blenheim.

The company was having difficulties finding people in Blenheim to work at the restaurant, and asked for help finding workers.

"If your story could be a call for staff we'd really appreciate your assistance," she said.

But customers have also blasted the restaurant's standard of food.

KFC customer Jeffrey Hynes said the pressure on staff meant the food was sometimes "absolutely dreadful".

Hynes did not blame the staff but those responsible for recruitment at Restaurant Brands, saying it was not uncommon to see only two or three workers manning the restaurant.

"You can't have an outlet like KFC with only two people serving," he said.

The shortage of staff had been a problem for the past two years and Hynes could not understand why it had not been fixed.

A sign in the window of the restaurant on Thursday said the front counter was closed "due to our staffing situation".

"I've spoken to a lot of people about it and the general consensus is that Marlborough deserves better than what we're getting."

He first became aware of the issue in 2014 after waiting for about 40 minutes for his order, before leaving the drive-thru line in frustration.

"That's the good thing about the Blenheim KFC, at least you can pull out of the drive-thru," he said.

Unite Union national secretary Gerard Hehir said they represented around 1800 KFC workers in New Zealand.

Unite had expressed their concerns to Restaurant Brands over staff shortages.

While staff would be paid overtime, Hehir said the practice of closing off parts of the restaurant was a last resort and there was a number of health and safety implications.

"It concerns us because this is a place where there are extremely hot vats of oil, so the person doing that cooking needs to concentrate and not do three other things at the same time."

"If you've only got two people, you can't run the restaurant, the drive-thru and do the cooking - it's impossible."

The other health and safety concern, aside from working long hours, was the potential for staff to be abused by customers for something that was not their fault, Hehir said.