British workers' most scandalous secrets

British workers have owned up to their most scandalous behaviour, from lying to feeding the boss laxatives.

In a survey by jobs website CV-Library, a third of workers say they consciously ignore the rules at their workplace, and four in ten have lied to the boss.

One fifth say they've been rude to a customer or client, and 12% that they've deliberately got colleagues in trouble.

"We spend a great deal of our time at work, so it's unsurprising that some employees will hit a rebellious streak every once in a while. Although these offenders are not true of every workplace, it's clear that some workers are knowingly acting inappropriately, and clearly aren't afraid of the consequences," says Lee Biggins, CV-Library's founder and managing director.

"But whilst white lies or taking credit for other's work may seem harmless, there could be bigger repercussions down the line. We often joke that rules are made to be broken, but if you want to do well in your job, and move ahead in your career, it's best to keep it professional at all times."

The 10 worst workplace confessions

1. John, an IT consultant from Manchester: After months of putting up with an obnoxious boss, I placed my resignation letter with a knife on his desk and very calmly said; "I found this in my back...I think it's yours!"

2. Ryan, a sales manager from Bristol: "I once slept with a customer behind a stage whilst a conference was taking place... and we got caught."

3. Michelle, an advertising executive from London: "There was a heatwave, but my boss said we weren't allowed to take any holiday, so I lied and told her that I was attending a funeral so that I could have a few days off in the nice sunny weather."

4. Jack, a shop assistant from Liverpool: "My boss had been annoying me so I fed him laxatives one morning and left after lunch for him to run the shop on his own. To this day he still thinks he caught a random stomach bug."

5. Mike, a waiter from Edinburgh: "I tried to play a practical joke on my colleague by putting a bucket of water on the staff room door, but it was my boss who ended up with water all over her new dress."

6. Lucy, a retail assistant from Brighton: "A customer was looking for a dress in a particular size but I wanted it for myself so I lied to her and pretended we didn't have it in stock."

7. Jake, a recruitment consultant from Lincoln: "It was near the end of the month and I was poor, so I stole loads of stationery and catering supplies for a party that I was hosting at the weekend."

8. Ben, a project manager from Bournemouth: "Things got rather heated with a colleague – he was really winding me up so I threw a stapler at him in rage!"

9. Katie, a finance assistant from Newcastle: "I once did lines of cocaine off of my manager's desk... he wasn't there and I obviously never told him what I got up to."

10. Howard, a construction worker from Essex: "Had a number two in my work mate's tool box... when you've got to go, you've got to go!"