Sir John Major received an increasingly torrid press during his time in Downing Street and is said to have taken newspaper criticism to heart.
The Sun famously switched its support from the Tories to Labour for the 1997 general election, when his premiership was brought to an end.
Labour deputy leader Harriet Harman will also be questioned at the inquiry today.
Yesterday former prime minister Gordon Brown, appearing at the inquiry, denied claims that he had “declared war” on Rupert Murdoch in a telephone call to the media mogul or behaved aggressively towards News International chief executive Rebekah Brooks.
He said the conversation where he was “alleged to have acted in an unbalanced way” as well as threatening Mr Murdoch “never took place”.
“I’m shocked and surprised that it should be suggested even when there is no evidence of such a conversation,” he said.
He also criticised the way the Sun published a story about his son Fraser’s cystic fibrosis, which he complained about last July.
The ex-Labour leader called for measures to stop the “conflation of fact and opinion” in the press.