Lord Grade is due to give evidence to the Leveson Inquiry into media ethics as the panel continues its scrutiny of the Press Complaints Commission (PCC).
The former boss of BBC, ITV and Channel 4 will appear in his role of PCC commissioner.
The press watchdog has been criticised by a number of witnesses at the inquiry , who have said the embattled organisation does not have enough powers to be effective.
Kate and Gerry McCann, Charlotte Church, Sienna Miller and JK Rowling have all told Lord Justice Leveson the PCC failed to protect them from alleged press harassment.
On Monday, former PCC director Tim Toulmin defended the body, insisting it is not a "formal regulator" but more of an "ombudsman".
"I think it's a complaints body," he added, "It's an industry coming together to create a complaints scheme really, I think, and so I don't think it's a regulator, no."
Also giving evidence today will be PCC chairman and ex-British ambassador to the US, Sir Christopher Meyer.
He will be joined by the new chairman of the PCC, Lord Hunt, who has been campaigning for a reform of the organisation.