The Labour leader told the Leveson Inquiry that News International’s market share, which, before the closure of the News of the World was estimated to be 37%, had given it a "sense of power without responsibility."

He said: "I don’t think we can divorce these questions of ownership, quasi-monopoly, or at least concentration of power, from the behaviour of some parts of the press

"I think we should have no worries of someone owning up to 20% of the newspaper market. I think there is then a question of between 20 to 30%. Where would you set a limit? That’s where I’m coming from, because I think it’s good for our democracy to have plurality in the market."

News International's current market share is estimated at around 34%.

Miliband also called the 2003 Communications Act "an analogue act in a digital age" which needed to be revised.

He said: "I think it will need to be updated, and I think then there’s a question about whether you should have an overall limit about how much control one organisation has on the market.

"My aim is not to stifle one particular organisation or another. My aim is plurality and a sense that one organisation does not exercise overweening power."