The information requested is not available centrally and could be obtained only at disproportionate cost.
The system used by the UK Border Agency to record data relating to prosecutions for immigration offences (including those found working in breach of their conditions) does not categorise individuals by the nature of their stay in the UK. To establish the number of foreign students prosecuted for this offence, therefore, would require the examination of individual records at disproportionate cost.
It should be noted, however, that the UK Border Agency would normally seek to remove an individual under such circumstances, rather than to prosecute them, as the former presents a more cost effective alternative.