Why are energy bosses being questioned?

Top executives from the 'big six' energy companies are answering MPs questions on Tuesday afternoon following recent price rises of an average of 9.1%.

Most of the energy firms have insisted the increases are mainly down to higher wholesale prices - but the regulator Ofgem says those prices have risen by just 1.7% over the past year.

So why the discrepancy? BBC business reporter Stephanie McGovern breaks down the figures.