Buying a new house is a positive experience and looked forward to by all purchasers. The Vendors too are looking forward to moving on to a different location.
The actual shift is the least enjoyable aspect. It is always difficult to manage and always under time constraints. Included in the scenario is often the situation where the Vendor runs out of time and energy to completely remove all rubbish from the property as they leave. Common sense tells us all what might reasonably be left behind, but what if there is an unreasonable amount remaining?
There is no legal obligation ultimately.
If you notice rubbish inside and outside when you are making your decision to buy, then on making an offer to do so, put a clause in the agreement requesting that the property being left in a tidy condition and rubbish free. This clause would normally be deemed a warranty.
So, while the purchaser cannot refuse to settle because of it, following the pre settlement inspection the purchaser may request that a compensation amount be retained until the rubbish is either satisfactory removed or those funds retained are used to do just that.