Defence Secretary John Reid has denied Conservative claims that the police had been "politicised" in the run-up to a terror vote.
He said the calls were a "smokescreen" to cover Tory embarrassment at blocking a 90-day detention period for terror suspects - they backed 28 days instead.
The Tories want an inquiry into alleged lobbying of MPs by chief constables.
The home secretary has admitted writing to Acpo, requesting senior officers be available to provide advice for MPs.
But Charles Clarke, in a letter to The Telegraph on Saturday, denied Conservative claims that this had amounted to the "politicisation" of the police.
The Conservatives allege the Association of Chief Police Officers (Acpo) were put under pressure to back Tony Blair's campaign to secure the 90-day detention, which was defeated by MPs on Wednesday.
Mr Reid accused the opposition of a "slur on the integrity of the police".
In a further development, Conservative Party leader Michael Howard has written to Tony Blair to ask whether the police need authorisation from the Home Secretary before appearing in the media.
The letter comes in response to remarks made by Mr Reid on BBC Radio 4's Today programme on Saturday, which appeared to suggest that every interview now needed specific approval.
But the Home Office has denied that anyone in the police force has to seek approval from the minister to do media interviews, adding that the police remain "operationally independent" of the government.
Mr Reid said that when the police or the armed forces were going to respond to requests from MPs, "or indeed to requests from the Today programme", the request was authorised by the Secretary of State.
Mr Howard's letter said: "That was certainly not the case when I was Home Secretary. When was this change instituted and at whose instigation?"
On the same programme Mr Reid denied the police had been playing politics, saying they had only being providing their expert advice on public safety, something they had done for governments of all persuasions.
"There was nothing wrong in this," he said.
"Where it involves matters of national security and what the police themselves think is necessary for their operational capability in counter-terrorism, the police are entitled to make their views known.
"Charles [Clarke] was entitled to ask them to stand ready so to do if they were approached by their local MPs."
He added that Mr Clarke had not dictated what the officers should say, or put pressure on them.
Conservatives Stephen Dorrell and Peter Lilley have tabled a parliamentary motion condemning ministers for "embroiling them in politics".
They say MPs received telephone calls, emails and letters from chief constables.
Sussex chief constable Ken Jones, who speaks for Acpo on counter-terrorism, wrote to police chiefs around the country last Friday, a day after Mr Clarke wrote to Acpo.
He asked them to make sure all of their MPs were informed about the argument for 90-day detention.
'Closeness to vote'
Meanwhile, the former chief constable of Humberside, David Westwood, said a damaging perception had arisen that police were trying to influence the parliamentary process.
"Giving professional advice and lobbying MPs for change is a normal part of policing... but there is a limit," he told Today.
"Police shouldn't become involved in the parliamentary process and nor should they be perceived to be involved.
"I don't think there's anything wrong with inviting MPs to consult their chief constable. The problem in this instance was the closeness in time to the parliamentary vote."
Tory MP Robert Key said that police chiefs may have been under undue pressure on the issue because of recently-published Home Office proposals to reduce the number of forces in England.
He added that during the 1984 miners' strike, the Poll Tax riots or road protests of the 1990s he had not experienced centrally-organised police lobbying.