The Liberal Democrat Deputy Leader Simon Hughes told ITV1's The Agenda that he is opposed to the statutory regulation of the press.
Lord Justice Leveson's report is published on Thursday.
The Agenda is on ITV1 at 10.35pm and at 11:35pm in Scotland.
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The talks descended into crisis on Friday when Canada's trade minister Chrystia Freeland walked out of meetings.
Police in New York are still investigating what the substance is and whether it could be harmful.
The Sherlock actor made the comment while he received an award for his humanitarian work.