Hi,
I've had a look at the Whirlpool site for detailed information for you, but they seem to want you to buy a pump assembly complete. Not very helpful.
If you type your exact model number they may come up with a spares kit -
Whirlpool Sapres Department -
http://www.4whirlpool.co.uk/cgi-bin/search.pl?query=pump&pg=9&brand=&model=&part=
There is usually a slight gap in this mincer arrangement. It could be that the "strainer" has become detatched from it's intended fixed position. If this is the case. Try heat from a soldering iron to bond it to it's fixing, or an epoxy adhesive as a last resort before purchase of a new pump assembly.
If there is room for a small spring on the output shaft, this may also keep it at the correct distance.
Sorry I could not identify the exact part for you.