US literary agent Andrew Wylie has accused a publishing company of acting in an "unusually shrill and punitive" way toward authors.

HarperCollins' parent firm NewsCorp is under pressure in the wake of the News of the World phone-hacking scandal.

Mr Wylie said recent events could "perhaps turn on some lights" and look at "what is proper behaviour and what isn't" at the publishing house.

A HarperCollins spokesperson said the claims were "extravagant allegations".

On Monday Mr Wylie, whose clients include Martin Amis and Philip Roth, told BBC Radio 4's The World at One programme that the publishing house had been under "unusual pressure" for a while.

He explained that 18 months ago he spoke to News Corp's deputy chief operating officer James Murdoch about his concerns.

"I told him I thought it was a family business and he needed to look after it a little more closely," Mr Wylie said.

When asked if he thought improper behaviour had been conducted within HarperCollins, he said: "I do. They have been, and I've explained this to the heads of the company in London and New York, unusually shrill and punitive towards authors."

But he refused to give examples, adding: "I don't want to go into those examples. But that has been my experience."

In a statement a HarperCollins spokesperson said: "Mr Wylie makes extravagant allegations to the BBC but fails to specify exactly what he is complaining about.

"The more mundane truth is that HarperCollins have had differences of opinion on business matters with Mr Wylie in recent times.

"Mr Wylie is a seasoned operator (there is a reason for his nickname The Jackal) but we are taken aback by his crude attempt to link a business disagreement with more serious matters."

News Corporation chiefs Rupert and James Murdoch and former executive Rebekah Brooks will be quizzed by MPs later about the phone-hacking scandal.