The complexity of energy bills is a major cause of confusion, significantly harming people's ability to get the most competitive deals, according to a think tank report commissioned by comparethemarket.com.

It has called on regulator Ofgem to make it a legal requirement for energy providers to send all customers an annual review notice, or 'trigger'. It says the introduction of such a system in the motor insurance market has been a key driver in increasing competition and lowering bills.