Speaking about the murder of Drummer Lee Rigby in Woolwich, Labour leader Ed Miliband said extremists will fail to divide Britain because "British people know this attack did not represent the true values of any community, including Muslim communities who contribute so much to our country".
Mr Miliband said he supported action to bring the perpetrators to justice and work to unite communities and learn the lessons of the attack.
But he questioned the Prime Minister on whether the events in Woolwich would mean further movement on controversial communications data proposals.
Mr Miliband said, "What is your current view on the need for legislation on communications data?"
Mr Cameron replied: "I think we need a frank debate in this House. There is a problem when, at the moment, some 95% of serious crimes involve the use of communications data.
"That is not the content of a fixed or mobile telephone call, it's about the nature of the call - when it was made, who was it that made it, when did they make it".
Police chiefs have revealed that anti-Muslim activity reported in the wake of Drummer Lee Rigby's death was mainly online abuse that peaked on the day after his brutal killing.
The Association of Chief Police Officers (ACPO) said 71 incidents were reported to its national community tension team over five days after Drummer Rigby's murder in Woolwich, southeast London, on 22 May.
Detective Chief Superintendent Steve Cotter, ACPO's lead on national community tension, said that although exact figures were "unclear", the number of incidents appear to have fallen now.
"The numbers of hate crimes did peak and they are now reducing," he said. "In the main, the ones that have been quoted are online ... it's people's opinions that people categorise as unpalatable."
Speaking at a briefing at ACPO's headquarters in central London, DCS Cotter confirmed a small percentage of the reported incidents were attacks on mosques and claims that Muslim women had their head scarves removed.
Two men accused of murdering soldier Lee Rigby have appeared in separate courts today amid tight security. Drummer Rigby, who had lived in Halifax with his wife and young son, was killed in London last month.
Michael Adebolajo, whose father's home in Saxilby near Lincoln was searched after the attack, made his first appearance charged with murder. In the Commoms today the Prime Minister said the Government would do all it can to tackle "poisonous ideology."
Bob Constantine reports
Michael Adebolajo, one of the men charged with murdering soldier Lee Rigby, made his first appearance in court today.
Holding a copy of the Koran, the 28-year-old told Westminster Magistrates' Court he wanted to be known as Mujahid Abu Hamza.
A second man, Michael Adebowale, also appeared at the Old Bailey via video link.
ITV News reporter Ben Chapman reports.
After standing when asked to at the end of his court hearing charged with the murder of Drummer Lee Rigby, Michael Adebolajo, asked Deputy Chief Magistrate Emma Arbuthnot: "I would like to alleviate the pain if I may?"
He then kissed the Koran and raised his arm into the air.
Woolwich suspect Michael Adebolajo has appeared in court charged with the murder of Drummer Lee Rigby.
He is also charged with the attempted murder of two police officers and the possession of a firearm.
The 28-year-old waved and smiled at a friend in the public gallery before being remanded in custody, ITV London's Ronke Phillips reports.
Woolwich murder suspect Michael Adebolajo has arrived at Westminster Magistrates Court for his first court hearing.
On Saturday, the 28-year-old was charged with the murder of Drummer Lee Rigby, after being released from hospital.
He has also been charged with the attempted murder of two police officers and the possession of a firearm.
Woolwich suspect Michael Adebolajo has become the second man charged with the murder of Drummer Lee Rigby, Scotland Yard said today.
Adebolajo has been remanded in custody and will appear at Westminster Magistrates’ Court on Monday.
Another man, 22-year-old Michael Adebowale, was charged with the murder of Drummer Lee Rigby earlier this week. He will appear at the Old Bailey on Monday.
Michael Adebolajo, 28, has been charged with the murder of Drummer Lee Rigby, Scotland Yard said today.
He has also been charged with the attempted murder of two police officers and possession of a firearm.