More creative industries such as marketing, PR agencies, or indeed businesses within the IT industry - tend to favour a more relaxed approach, I guess there is nothing wrong with this and in some respect it is expected. However as an employer, if you wish your workers to wear more business orientated attire then it is important that you stipulate this within a dress code policy. Whether this is wearing a shirt and tie or a suitable dress appropriate for the professional image of your business, you need to outline what you expect within your HR policies and procedures. Clearly this needs to be communicated to all staff and obviously new starters. You will need to set out action taken against those who breach the rules. Policing dress code rules will be something your management team will need to monitor and in most cases, it will require common sense action. However, there will be times when certain dress code will be questionable and a firm but fair approach will need to be taken. Remember you can only dictate dress code rules providing you have policies in place to do so – make sure that they are communicated to all employees accordingly.
Does the professionalism of staff depend on whether they are wearing a suit or not? Well there seems to be some debate on whether wearing a suit or smart business dress is being phased out in favour of a more casual dress code. Personally I think it depends on the nature of the business such as whether you are customer facing or not.