By Mike Powell Business reporter, BBC News

Pret A Manger has received thousands of complaints over its drinks subscription service following frustration that not all promised beverages are available.

The £20 a month deal offers unlimited hot and cold drinks.

But the BBC understands the High Street chain has received 5,000 complaints about the offer, such as smoothies often being unavailable.

Ex-Pret staff have also told the BBC its introduction has meant workers feel overwhelmed by the increased workload.

Pret a Manger launched the subscription in September 2020 after sales plunged during Covid lockdowns.

The company said it was "really pleased" with the response to the subscription offer where it pledges: "If our Baristas brew it, blend it or steam it, you can have it!"

"While it's been incredibly popular, we're constantly working with our teams and customers to make it better, so that we're able to continue to deliver the outstanding service our people are known for," the company said.

But some customers said that this is not always the case.

Rachel, from Watford, who had been on furlough for months, recently started commuting again. "As I was now travelling into London again I thought I'd treat myself to drinks I wouldn't usually try," she told the BBC.

"But most of the time I'm told that I can't have a cold drink because they're unavailable."

Another customer, Brendan, also subscribed, limiting himself to two drinks a day "to stay healthy". But he told the BBC that by mid-afternoon mango and pineapple preference is often not available.

"It's become a long standing joke with the staff now," he said. "I laughed it off for a while, but now I'm getting angry and I'm starting to feel I've been ripped off`."

Meanwhile another customer, Isabelle, tweeted: "Have been to four Prets this morning that have 'stopped doing smoothies'. Is this because of the subscription? The smoothies were a key part of me wanting to sign up."

Other customers have taken their complaints to the UK's Advertising Standards Authority (ASA).

The regulator has contacted Pret a Manger to say that they should "consider reviewing the ads for their subscription service".

The ASA said it informed Pret "that their ads should not state or imply that the service was available in all store locations, or that it covers their entire range of products if that wasn't the case".

Pret said: "We have spoken with the ASA to ensure all Pret marketing for the coffee subscription is in accordance with their latest guidance."

Meanwhile, some former Pret employees said working conditions became "unbearable" after the subscription was launched.

One claimed that staff deliberately turned blending machines off as it takes one-and-a-half minutes to prepare a smoothie.

If a "mystery shopper" is in store they'll be marked down - with the team missing out on financial bonuses - if they don't deliver drinks within a strict time frame.

He also alleges that other colleagues pretend the machines are broken, are being washed or there's a supply issue and they've run out of the small blue bags which contain a carefully portioned amount of fruit.

"Staff are just frustrated and tired with the endless smoothie and frappes giveaway, and they just boycott it, " he said. "It is just easy to say that ice or smoothies or frappe are gone for today.

"They are really time consuming. Try to make 50 smoothies daily one by one and you will feel it."

A Pret barista who recently quit revealed that he had worked for his store in the Thames Valley since it opened three years ago: "But the whole demeanour changed when they brought in the subscription. The blending machines can't take it.

"I can understand why Pret think it makes commercial sense but the staff can't take much more."

Another Pret worker was so disgruntled with the conditions that she set up a website to gather complaints. The site, expret.org, is kept up to date with the latest frustrations, as she felt no one was listening to her or her colleagues.

Pret claims that less than 1% of the complaints about their subscription are about the lack of smoothies or frappes.

A spokesman added that when Pret suggested frappes and smoothies would be removed from the subscription earlier in 2021: "There was a public outcry so Pret listened and kept them as part of the subscription."

In the same month Pret launched the deal, rival Leon offered a similar promotion for £15 a month - but it was limited to 75 coffees a month and excluded other drinks such as teas and hot chocolate.

Leon has since suspended it, stating: "To help our teams during these difficult times, we have stopped taking on new subscribers."

Pret to hire 3,000 staff as city workers return

Pret a Manger makes staff pay cuts permanent

FBI took top secret documents from Trump's home

Rushdie on ventilator and may lose eye after attack

Rushdie attack suspect charged with attempted murder

Evacuated twice in a summer as France's fires burn

We fled the Taliban for our Olympic dream. Video We fled the Taliban for our Olympic dream

Ibiza: The birth of the 'party island' Video Ibiza: The birth of the 'party island'

Meet the Indians named lockdown, freedom and emergency

Predicting Russia's next step in Ukraine

The mystery deaths of two Saudi sisters in Sydney

Salman Rushdie: The writer who emerged from hiding

'I'm a different person after having monkeypox'

The world's first long-distance car journey

The best public pools around the world

Why open relationships are on the rise

The ejector seats that fire through the floor

© 2022 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.