Expert View: You can grass yourself up and you still won't get the sack

Ask your boss: would you be sacked for committing a crime? Possession of cannabis? Hitting a stranger in the street? Giving a bribe? They might have tried dope in their student days but no one has suggested that the smokers, jokers and midnight tokers who make up a sizeable minority of the Cabinet aren't safe in their jobs. The same might not be true if they were caught smoking today.

Maybe the liberal, university-educated nature of the crime makes it something you can admit to without worrying the boss unduly. Some crimes are more serious than others and the stigma attached to cannabis doesn't register on most scales.

The "spent crimes" rules under the Rehabilitation of Offenders Act prevent sackings based on old convictions, but it's a fair bet resignation would follow for lots of other crimes that surface long after the event.

Your boss is likely to be lenient if the crime was committed a long time ago when you were young and foolish, didn't know better, everyone was doing it and you now see the error of your ways. Not surprisingly, it cuts no ice with magistrates if the offender's only excuses are that he is young and foolish, etc etc; he still gets a criminal record. Sadly, it doesn't make it easier for magistrates to ram home the message that cannabis carries mental-health risks when people who have reached the very top of their careers parade their past pot smoking across the media with impunity.

Nine years ago, a postal worker was banged up for 40 days in France for thumping a rival supporter at the football World Cup. He was summarily dismissed by the Post Office but won his case for unfair dismissal. The criminal behaviour took place in the worker's own leisure time and didn't have an impact on his job, so the only question the Employment Tribunal had to consider was whether the incident damaged the reputation of the Post Office and could therefore justify instant dismissal. The tribunal decided it didn't and therefore the Post Office was wrong to sack him. Clever analysis, but the wrong result for society.

Most employers can to sack workers on the spot for gross misconduct at work, such as punching the boss. But you can't always dismiss someone for punching in their own time.

In the City, drug taking and other activities carrying a reputational risk are usually dealt with in staff members' contracts, rather than being left to the discretion and unpredictability of the courts. The pragmatic position for the employer is that no worker with two brain cells and the desire for future employment is ever going to take issue with being sacked for taking illegal drugs; he or she would never get another job in the City if this type of dirty linen was aired in a public tribunal.

How would your boss feel if you confessed to having fingers in the till 20 years ago? Crimes of dishonesty – fraud, embezzlement, theft – do not go down well. In almost every job, if an employee is found to have committed such a crime, he or she will almost certainly be sacked as soon as there is incontrovertible evidence or an admission of guilt. No one takes these cases to tribunals to fight over the dismissal being unfair; for many, the sack and the absence of a reference are the only real punishments. Few businesses involve the police and there must be many thousands of thieves and embezzlers out there who are grateful their old firms decided that bringing charges was not worth the time and effort.

So nicking isn't good for a career but skunk and violence remain as possible leisure activities. They aren't recommended for Cabinet ministers.

Alasdair Douglas is senior partner and head of corporate tax at City law firm Travers Smith. <</i>a href="mailto:alasdairdouglas@traverssmith.com">alasdairdouglas@traverssmith.com