AC losses have been measured on HTS tapes in presence of both AC transport current and AC magnetic field, by using an extended bolometric technique. Tapes as long as 10 cm are thermally anchored at its ends to the 77 K bath, and are placed in a chamber where the spurious effects due to thermal instabilities are strongly reduced. The AC power losses are rapidly obtained by measuring the resulting temperature gradient between the centre and the extremities of the sample, with a sensitivity of ∼1 μW/cm. In this way, the losses can be measured at various frequencies, phases and amplitudes of the AC current (up to ∼40 A) and field (up to ∼600 mT), which are in fact completely independent of each other.