David Cameron is unhappy with the prime minister's stance on the arrest
David Cameron has challenged the prime minister to do more to distance himself from the arrest of MP Damian Green over Home Office leaks.
Writing in the News of the World, the Tory leader said Gordon Brown's stance so far was "not good enough".
Meanwhile, a Scotland Yard spokesman has denied allegations police tried to "entrap" Mr Green before his arrest.
The Tory party refused to comment on this and other reports that members often checked their offices for bugs.
Gordon Brown and the Home Secretary Jacqui Smith have denied any "prior knowledge" of the arrests, saying the matter was one for the police.
Ms Smith is due to appear on the BBC's Andrew Marr programme on Sunday morning, where she is expected to be questioned about the affair.
In his opinion piece, Mr Cameron said the prime minister made his name through Whitehall leaks and unless Mr Brown spoke out, he would be guilty of "hypocrisy".
"The question is: does he think it is right for an MP who has apparently done nothing to breach our national security - and everything to inform the public of information they're entitled to know - to have his home and office searched by a dozen counter-terrorist police officers, his phone, blackberry and computers confiscated, and to be arrested and held for nine hours?" he said.
Mr Cameron described the arrest of the shadow immigration minister as a "watershed moment" and claimed "the right of one and all to hold the government to account is at stake".
He wrote: "On the rights of MPs to hold government to account, of course no one is above the law but in a democracy there is an important line to be drawn when it comes to acting in the public interest."
Meanwhile, the Mail on Sunday has reported that senior Conservative sources believe police tried to entrap Mr Green using a Home Office mole.
They allege that phone calls made by the man, who is named in the newspaper, were monitored by police as part of a "heavy-handed" attempt to "snare" the shadow minister.
Mr Green was not charged with any offences following his arrest
However Mr Green "declined" to be drawn into conversation with the whistleblower, who was also arrested 11 days ago.
A Scotland Yard spokesman told the BBC: "We strongly refute any accusation that any police officer has acted improperly."
The Mail on Sunday also reported that the mole had been re-housed by the Home Office to avoid media attention.
But the Home Office refused to confirm this and a spokesman told the BBC the government would not comment on an issue that involved the welfare of a member of staff.
The Independent on Sunday has separately reported that offices of senior Tories, including Mr Green, were routinely swept for electronic bugging devices as they feared they were being spied on.
Ben Wallace, the Conservative MP for Lancaster & Wyre, told the paper he had written to the prime minister requesting an urgent review of the Wilson doctrine - the convention that prevents MPs from having their phones tapped but not from other covert surveillance devices.
But a Conservative spokesman told the BBC that the party "did not comment on security measures."
Mr Green was not charged with any offence after his arrest on Thursday but was released on bail until February, when he could face further questioning.
The Ashford MP, the Tories' immigration spokesman since 2005, has denied any wrongdoing and said "opposition politicians have a duty to hold the government to account".
John O'Connor, former head of the London police unit, the flying squad, told BBC Radio 5Live he found it difficult to believe the government didn't know about the investigation.
He said: "If the prime minister and the home secretary were unaware of this police activity - then they must be utterly incompetent.
"And if they were aware of it then that makes them really quite dangerous. So I think whatever way, whatever path they choose it doesn't put them in a good light."