Ryanair cabin crew have been told they will face disciplinary action if they fail to sell scratchcards, perfume and alcohol on flights, with those under-performing stripped of their fixed rota and handed shifts on a week-by-week basis.

In a letter to a member of staff contracted to work for the low-cost airline by agency WorkForce, an unnamed flight attendant is told that their average “spend performance” was 48 per cent below budget across 251 flights before detailing their failure to sell a range of goods in the period from April to November, including cosmetics, fragrances, gifts and snacks.

“On 100 per cent of the 251 flights in this period you operated you sold no cosmetics,” the letter, seen by the Telegraph, says. “On 73 per cent of the 251 flights in this period you operated you sold no scratchcards… On 86 per cent of the 251 flights in this period you operated you had revenues of less than €50.”

The letter, signed by Grace Meehan, deputy HR manager, reads: “This performance is not acceptable and it is clear that you are simply not doing your job onboard.

“Whilst there may be occasions from time to time where circumstances prevent you from providing service in the cabin to our client airlines customers (turbulence, medical emergencies, etc.) this simply cannot be the case given the vast number of flights where you have drastically underperformed.”

Ryanair has had a tumultuous year Credit: 2007 AFP/JENS-ULRICH KOCH

The member of staff is then told that as a result of their “productivity” they will be losing their “5/3 roster” - five days on, three off and described by the agency as the “best roster in the business” - that their shifts will be designated “on a weekly basis to accommodate whatever gaps are necessary in your base”.

It adds that the cabin crew member's performance will be “closely monitored over the next two months” and “if there is no significant and sustained improvement then further action will be taken and you may be subject to disciplinary proceedings”.

The letter informs the member of staff of the importance of ancillary revenue to Ryanair. In July a study of such additional charges and sales found that Ryanair earned the sixth most in the world, with a total of £1.5billion of revenue in 2016 - up from £1.3billion in 2015 and more than a fifth of total revenue.

The Irish trade union Impact told the Guardian the letter made for “grim reading”, adding that the “primary role of cabin crew is flight safety”.

A spokesperson for Ryanair said: “While we cannot comment in detail on the WorkForce letter, it clearly does not set any ‘targets’ which must be met.

A spokesperson for Ryanair said staff do not have 'targets' Credit: Getty

“As the letter makes clear, any individual, who consistently, and markedly, underperforms, may face disciplinary proceedings ‘if there is no significant and sustained improvements’.

“We expect underperformers to improve, and they are given time and training to do so.”

WorkForce has been contacted for comment.

In the wake of the scheduling crisis Ryanair suffered in September, a flight attendant working for the carrier told Telegraph Travel that crew were planning a walkout over working conditions.

Another member of staff made allegations about a number of startling working practises at the airline, including only being paid for “flying time”, charging staff full price for water and sandwiches, and encouraging members to compete against each other for in-flight sales.

The airline did not respond to specific details of the article but said that its cabin crew earn up to €40,000 (£35,500) a year and “enjoy great terms and conditions including job security... a legal max of 900 flight hours per annum... [and] great sales commissions”.