Acting Labour leader Harriet Harman has said there was a "great deal of concern" over the appointment of former News of the World editor Andy Coulson as Downing Street's communications chief.
In a direct attack on David Cameron she said the Prime Minister's decision to appoint Mr Coulson "at the heart of Downing Street" was a reflection on his judgment.
Claims that MPs' phones were targeted are set to be investigated by the powerful Commons Standards and Privileges Committee, which Ms Harman said was an indication of the strength of feeling about the issue in the House.
Ms Harman told BBC1's Andrew Marr Show: "Last Thursday, without a vote because nobody opposed it, the House of Commons agreed to refer the question of phone hacking of MPs' phones and intercepting their phones to the Standards and Privileges Committee.
"If you saw what was said last Thursday it was Conservatives, Nadine Dorries and Nicholas Soames, it was Lib Dems like Simon Hughes as well as Labour people protesting.
"I think the fact that Andy Coulson is director of communications chosen by the Prime Minister is a reflection on David Cameron's judgment."
She added: "I think that there is a great deal of concern that at a time when obviously, and the Information Commissioner said this, that interception of phones of MPs was rife, that the Prime Minister chose a Fleet Street editor whose paper was involved in this, to put him at the heart of Downing Street."
In 2007, ex-News of the World royal editor Clive Goodman and private investigator Glenn Mulcaire were jailed for intercepting voicemail messages left for public figures.
The row has been reignited after a former reporter claimed Mr Coulson - editor of the Sunday paper at the time - was aware such eavesdropping was happening.
Mr Coulson, who resigned as editor in the wake of the court case, has repeatedly denied the allegation and Downing Street insists he retains the Prime Minister's confidence.