Phone-hacking campaigner Tom Watson has said there is "no chance" he will quit his role on the committee investigating the scandal.
John Whittingdale, who chairs the Culture, Media and Sport Committee, said Mr Watson's recent appointment to the Shadow Cabinet had created a conflict of interest.
But Mr Watson said: "It is bluster from a small group of Conservative MPs that are worried about this.
"When they were in opposition they had shadow spokesmen serving on select committees."
The West Bromwich East MP, who was made deputy party chair during the recent Labour reshuffle, said he would definitely take his place at the committee on November 10 when News International executive chairman James Murdoch gives evidence for a second time.
He said: "I don't have frontbench responsibility for the Department for Culture, Media and Sport. I will definitely be there. There is no chance this is going to stop me from being involved in the hacking inquiry."
Mr Whittingdale is powerless to change the committee's membership as appointments are in the gift of the political parties, but he has spoken to Mr Watson to make his views known.
Speaking earlier this month, he said: "Select committees need to be independent so should be confined to backbenchers. If he is a member of a select committee and a member of the Shadow Cabinet there is a conflict of interest because frontbenchers are bound by the party line.
"The Liaison Committee (made up of select committee chairs) has made it very clear that appointments should be made from backbenchers.
"He should step down and it may be that he decides to step down once the phone-hacking inquiry is completed."