My favourite measure of bias across the Beeb is the super-average interruption coefficient - which is calculated very simply by adding up all the individual I.C.s for each party & then dividing them by the number of interviewed granted to each party that month. As with all statistics, the larger the sample, the better the result - and the more significant any differences (hence the increase of the I.C. to 2 decimal places).
Here is how things worked out in December 09 - and it's the same old story!!!:
UKIP (2 interviews) - 1.55
Conservatives (56 interviews) - 0.75
SNP (3 interviews) - 0.70
Labour (99 interviews) - 0.46
Liberal Democrats (33 interviews) - 0.34
Plaid Cymru (1 interview) - 0
Independent (2 interviews) - 0
That very high average for UKIP, though based on just two interviews, leaps out straight off (and is not untypical), but then so does the fact that Conservative politicians are significantly more likely to be interrupted by BBC interviewers than Labour and Lib Dem ones - as shown here month after month after month. Left-wing bias at the BBC? Clearly.