Paul Dacre, the Associated Newspapers editor-in-chief, had a hand in the drafting of the Daily Mail publisher's statement accusing Hugh Grant of "mendacious smears", the Leveson inquiry has heard.

Dacre was one of a number of Associated executives involved in drafting the defiant statement, issued in November following Grant's claim that the Mail on Sunday could have hacked his phone, which accused him of "mendacious smears driven by his hatred of the media".

"The draft was contributed to by a number of people, including the editor-in-chief [Paul Dacre]," Liz Hartley, Associated's manager of editorial legal services, told Lord Justice Leveson on Wednesday afternoon.

In a tense exchange on the subject lasting more than an hour, Hartley said that in her view the group would "stand by" its "mendacious smears" allegation. She added that the group denied his allegation, made on the opening day of the inquiry on 21 November, that the Mail on Sunday could have hacked his phone.

She added that Associated also denied Grant's claim that the Daily Mail could have obtained information about the birth of his child through an unethical leak from the hospital.

However, Leveson said he was concerned that the response of Associated Newspapers was to say Grant had lied under oath.

"Mendacious smear, some would say was going miles too far," he said. "You respond by accusing him of perjury."

"Mendacious smear means 'deliberately false'," Leveson added. "The question is whether all this permits a deliberate dishonesty, which is equally a very serious allegation to make about anybody giving evidence under oath."

Associated conducted an eight-week internal inquiry into Grant's allegations, submitting its conclusions to the Leveson inquiry on Wednesday.

In its statement, Associated denied his allegation that the Daily Mail had found out he had become a father from a member of staff at the Portland Clinic, revealing that it had obtained this information from the Westminster Register Office.

Hartley also said that the Mail on Sunday diary and royal editor Katie Nicholl and a freelance journalist "emphatically denied" they had got the story regarding a plummy-voiced female film executive and Grant from phone hacking.

In November during his appearance before Leveson, Grant referred to the report, in the Mail on Sunday in February 2007, which said his relationship with his then girlfriend, Jemima Khan, was "on the rocks" because of "persistent late-night phone calls with a plummy-voiced executive from Warner Brothers" – a story he said was "completely untrue".

Grant told the inquiry: "I cannot for the life of me think of any conceivable source for this story in the Mail on Sunday except those voice messages on my mobile telephone."

He added: "I would love to hear what the [Mail on Sunday's] explanation of that is, if it wasn't phone hacking."

On the day Grant gave his evidence the Mail on Sunday issued a statement saying it "utterly refutes" the claim, adding that the information came from a freelance journalist who was "regularly speaking to Jemima Khan". Khan responded on Twitter saying the Mail on Sunday's account was "not true" and that the source "close to me must be psychic" because she "knew nothing about [the story] till it was in the paper".

Hartley told the inquiry on Wednesday that Grant should not have made such serious allegations without being in possession of the full facts.

"If you are going to make a serious allegation and you are leading a campaign against the media which Mr Grant is doing, you would and should take care over what you say," she added. "To make a number of serious allegations against us on something as thin as this was not something that should have been done."

The inquiry's counsel, Robert Jay QC, repeatedly asked her whether it was not "reasonable" for Grant to have drawn the conclusions that there was a leak at the hospital or that someone might have been listening to his voicemail messages.

She said she could see the logic of this, but that the allegations were so serious they should not have been made.

David Sherborne, the counsel representing alleged victims of press intrusion at the inquiry including Grant, asked Leveson whether he would be calling the individual journalists – Nicholl and the freelance – who had supplied the plummy voiced story to testify. Leveson said he would consider this.

Sherborne suggested that it would be for Dacre to explain why Associated was sticking by its "mendacious smears" comment when he appears before the inquiry on 6 February.

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