Trefor
The UKBA site states that,
"In the test, you will need to demonstrate a basic command of English (speaking and listening) at level A1 of the Common European Framework of Reference Someone assessed at level A1 can understand and use simple, everyday expressions and very basic phrases.
You will not need to demonstrate your reading and writing skills. The minimum standard that you must meet is in speaking and listening at level A1 of the Common European Framework of Reference. "
A1 level is very basic.
IELTS does not actually test at A1 level but at the slightly higher B1 level.
The pass score for the IELTS B1 level is 4 when applied to requirements for a UK visa