Boron nitride nanotubes (BNNTs) are stable at high temperatures and by controlling their electronic properties, their range of application will be greatly increased for development of nanoelectronics devices. By the employment of tight binding model with the Green function approach and the Kubo-Greenwood formula, the effects of the transverse electric field on the electronic and thermal conductivity [κ(T)] of carbon doped single-walled BNNTs have been investigated. The studied structures are included a carbon atom placed instead of a boron [CB] or nitrogen [CN] atoms. The positions and intensity of DOS peaks are affected by the electric field strength and location of dopant atom θ. The band gap decreases with F and the semiconductor-metal transition occurs in critical electric field Fc. The κ(T) is zero below 1500 K due to wide band gap and it becomes non zero in presence of electric field and The stronger electric field shows larger κ(T). Unlike to CN type, in the CB type in presence of the electric field, κ(T) decreases with increasing the θ and the κ(θ=0o) [κ(θ=180o)] has largest [smallest] strength in T < 1500 K. In the T < 1500 K, all structures have the Lorenz number [L(T)] with peak intensity LMax at the TM, independent to the field strength and angel θ. The intensity and position of the L(T) peak are dependent on the F and θ and for CB (CN) structure, the LMax and TM increase (decrease) by increasing the θ angle. From these calculations, it can be concluded that the thermoelectric properties of BNNTs can be significantly modified by carbon doping and electric field and the results can be used to predict and enhance the thermoelectric properties of the BNNT based nanoscale devices.