Should garden designers take commission payments?

We were recently offered a commission payment by a firm that designed and built treehouses. We were recommending them on a large garden we are undertaking in Surrey. We did not take up the offer. Interestingly, shortly afterwards they put us forward for another job in the same neighbourhood and demanded a commission payment if we were appointed. We refused, saying that payment should be unnecessary. This resulted in quite a row between us.
We were against taking the payment on a number of different grounds. Firstly, it clouds your judgement. I want to be free to make decisions on a number of criteria, without the ‘size of the bung’ being one of the factors. Secondly, we should be free to recommend others (and be recommended ourselves) on the basis of competency, skills and experience. We work with a range of other experts and specialists – joiners, artists, lighting designers, etc. we choose them on merit. Finally (and most importantly) it is essentially dishonest. Not dishonest in the sense of illegal, but more in the sense of not being transparent. If you take such payments, do you tell your client? If not, why would that be? In other industries (such as the insurance industry), we all rail against similar opaque practices, calling them shady, dishonest or even corrupt. When it is us being offered the money it is a slightly different story. We either defend it saying it is an honestly earned commission, or keep quiet and take the money (which is what I suspect most people do). Even if one decides to take a stance on this, it is very difficult not to acquiesce when a supplier effectively gives you the money unbidden by inviting you to invoice them, as happened to us recently. Perhaps weakly, I didn’t invoice them, but I didn’t tell them I wouldn’t take the money either (although I won’t). I am not saying we haven’t accepted it once or twice in the past, but we have made a joint decision in the business to draw a line here.
In any case, most if not all professional associations frown upon the idea: it is strictly forbidden by the code of professional conduct of both the Landscape Institute and the Society of Garden Designers. I suspect that this does not stop the practice going on however. I also realise that I will probably unleash a flood of posts from other designers saying that this is the only way they can make a decent living; that it is alright for you lot in the SE etc. etc. My answer to that is that you should charge more. Again – ‘Alright for you lot in the loaded South-East’. But if you don’t try and charge a living wage for what you do, how will clients ever learn to value it? What clients pay for should be transparent and fair – to both sides.
John Wyer