The stars of the massively popular US sitcom The Big Bang Theory are seeking substantial pay rises.

Deadline reports that Jim Parsons (Sheldon), Johnny Galecki (Leonard) and Kaley Cuoco (Penny) are currently earning $350,000 (£217,700) per episode - but now they want over $500,000 (£310,950) each.

Co-stars Mayim Bialik (Amy) and Melissa Rauch (Bernadette) have already been given a pay increase, with their salaries expected to double to around $60,000 an episode.

Meanwhile, Simon Helberg (Howard) and Kunal Nayyar (Raj)  - who are negotiating as a pair - are also seeking pay bumps, with the duo currently earning $125,000 and $75,000 per episode respectively.

The negotiations are for a potential eighth season of the show, which has yet to be officially commissioned by CBS.

The seventh season of The Big Bang Theory starts on CBS in the US on September 26 and will subsequently follow on E4 in the UK and in Ireland on RTÉ Two.