The leaking of the names of a string of high-profile recipients of awards in the new year honours list is to be the subject of a Whitehall inquiry.

The gongs for actors including Sheridan Smith, John Hurt and Joan Collins were among those widely trailed in press reports several days before they were due to be made public late on Tuesday evening.

According to convention, recipients are told they are to receive an honour several weeks before the list is published and are then sworn to secrecy.

Sir Bob Kerslake, the outgoing head of the Civil Service, said the leaks were “highly regrettable” and the high number of names put into the public domain was particularly concerning.

There is no suggestion that any of those honoured has let slip their secret and attention is likely to be focused on Whitehall and others who are made aware of the embargoed list.

New Year Honours 2014

Sir Bob said: “I think it’s unfair on the individuals who are asked, indeed instructed, to keep the fact that they are recipients of awards confidential.

“I can’t comment on where they are coming from. We will look into it, I’ll leave it at that.”

He added: “There have been leaks in the past but there was, on this particular occasion, a significant number and that’s the point we will look into.”

The leaks also included names who are not in fact receiving honours, among them the rugby player Jonny Wilkinson who was supposedly to receive a knighthood. He appeared to acknowledge the speculation when he posted on Twitter: “So many more deserving amongst u who won’t get recognition.”

Sir Bob said: “It’s particularly unfair when names get quoted in the papers who then subsequently aren’t on the list. In every sense it’s highly regrettable and we will look into this.