The Director of Public Prosecutions insists that his office — not the Attorney-General — will make the final decision on whether to bring charges over cash-for-peerages.

Sir Ken Macdonald, head of the Crown Prosecution Service, said that Lord Goldsmith was “entitled to be consulted if he wants to be”.

But he told The Times: “We are going to make the decision. If the Attorney-General wants to be consulted, of course we will consult him. But the decision will be made here.”

Lord Goldsmith has refused to stand back from any decision to prosecute. Were a decision to be taken not to prosecute, he said, he would consider how best to ensure that the reasons were explained.

Peerages inquiry: we decide

Sir Ken Macdonald talks to Frances Gibb about cash for honours, tackling knife culture and broadcasting trials on TV

In the interview Sir Ken also called for:

* A community-wide response to tackle knife culture

* Some trials to be broadcast on TV

* The mandatory life sentence for murder.

The DPP was giving his first interview with a national newspaper since reports last month of his relationship with an attractive young criminal barrister. Sir Ken, 54, who was knighted in the New Year Honours, refused to discuss the allegations or to say whether or not the relationship was still on.

“I don’t talk about my private life or anybody else’s. I don’t want to talk about it,” he said.

Instead he made clear it was “business as usual” and top of the CPS intray is the cash-for-peerages investigation.

Sir Ken has stepped back from any personal involvement in the decision because he was a member for three years of Matrix Chambers along with Cherie Booth, and so “shared a commercial interest”.

“She is the wife of a potential witness,” he said.

The decision therefore falls to Carmen Dowd, head of the special crime division at the CPS, although Lord Goldsmith, who is Sir Ken’s boss, has said that he expects to be consulted.

Lord Goldsmith’s view that he should play an “active part” has prompted suggestions of a potential conflict of interest. His stance has also put him at odds with Lord Falconer of Thoroton, the Lord Chancellor, who told the Constitutional Affairs Committee that the decision was for the CPS and that the Attorney-General “would not interfere in the normal course of decisions being made.”

But in an exchange before Christmas, Lord Goldsmith said that the Lord Chancellor was not in a position to give “an assurance” as to how he, the Attorney, would act. He insisted that it would not be “right” for him to stand aside from involvement in the case.

Commenting on a range of issues, Sir Ken went on to call for a “community-wide” response to recent stabbings.

“It’s something that police and prosecutors can’t deal with on their own,” he said. He added: “It’s a very serious crime and we need effective prosecutions and punishments but the thing is to stop young people carrying knives.”

He said that he favoured allowing cameras into courts, perhaps to broadcast appeals, as was tested in a pilot last year.

But he said: “I don’t think we want to have TV cameras of witnesses being cross-examined, because I think you might get people grand-standing; you don’t want film of juries nor an O. J. Simpson situation.”

He reiterated his view that if the law of murder is reformed to introduce new categories, then the mandatory life sentence should be retained for first-degree murder.

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