As of today (7 April, 2014), both the theory and practical driving tests are only available in English or Welsh. This is a change that was called for by 70% of respondents to public consultation by the then DSA (now DVSA). Previously candidates could take their car and motorbike theory tests with a voiceover in one of 19 foreign languages, and use interpreters on theory and practical tests. This gave rise to a number of fraudulent operators who assisted candidates with what answer to select rather than directly translating.
As all our road signs are in English or Welsh, it doesn’t make sense to have tests in languages other than English and Welsh.