Mike for clarity and following UKBA information, even though a person may be required by the provider to sit all four components of an IELTS test, they would meet the English language requirement by gaining a score of a minimum of level 4 in speaking and listening. Even if they failed the reading and writing components and overall their final score was less than 4.
for example:-
Reading = 1.5
Writing = 1.0
Speaking = 4.0
Listening = 4.0
Overall IELTS score = 2.5
Here. the applicant is able to demonstrate they scored level 4 for speaking and listening in an approved test by an approved provider therefore an applicant could use such results to meet the English qualification for partners.