Labour has called on Prime Minister David Cameron to disclose all his communications with former News International executive Rebekah Brooks, amid claims that a tranche of emails and text messages between them has not been handed over to the Leveson Inquiry.
The demand came after Mr Cameron refused to answer a question about the messages in the House of Commons.
In a letter to the PM, shadow culture secretary Harriet Harman said it was "vital" that Lord Justice Leveson's inquiry into media standards has all the evidence available, and called on Mr Cameron to hand over all his communications with Mrs Brooks and former News of the World editor Andy Coulson.
The Independent reported earlier this week that there were dozens of emails which have not been released to Lord Justice Leveson as part of his inquiry, which was prompted by allegations of phone-hacking at the News of the World. But Downing Street insists that it has handed over all the material requested from it.
Mr Cameron's official spokesman told reporters: "We have given the Leveson Inquiry the information that they wanted, the relevant information."
But Ms Harman told the PM in her letter: "In order for the public to have total confidence it would be preferable for you to disclose all of the emails and let the Leveson Inquiry decide which are relevant."
The Labour deputy leader later said: "The reports that the Prime Minister has not made a full disclosure to the Leveson Inquiry are deeply concerning.
"The Prime Minister set up the Leveson Inquiry to examine the culture, practices and ethics of the press including the relationships between the press and politicians. It presents an historic opportunity to solve long-standing problems with the press and it is therefore vital that the Leveson Inquiry has all of the evidence available.
"In order for the public to have total confidence, David Cameron should disclose all of his communications with Rebekah Brooks and all of his communications with Andy Coulson and let the Leveson Inquiry decide which are relevant. I have therefore written to the Prime Minister urging him to do that."
Mrs Brooks resigned as chief executive of News International over the phone-hacking scandal last year, while Mr Coulson quit as director of communications at 10 Downing Street.