A few weeks back, U.K. Deputy Prime Minister Nick Clegg announced he would block extensions of the monitoring powers of U.K. intelligence and law enforcement agencies because he agreed with critics who complained they amounted to a "snooper's charter".

Such decisions might now backfire on political leaders as voices start to call for closer communications monitoring in the wake of last week's savage Islamist terror attack on a British soldier on a Woolwich, London street.

One of Clegg's own party, House of Lords Peer Lord Carlile, went public Sunday in an article in the populist Mail that the law Clegg vetoed, the Communications Data Bill, would have been "very likely" to prevent attacks of this kind in the future.

[ What are other ways terrorists slip through the cracks? Read How Foreign Names Trip Up Terrorism Databases. ]

Carlile's attack is made more potent by his claim that he wrote to Clegg immediately after the latter's move to warn him, "I fear that this [blocking of the Bill] may come to haunt you and the party if any terrorism event occurs which could otherwise have been avoided."

Clegg's critics argue that the interception of Web and email communications data traffic as proposed would have alerted authorities to plans by the terrorists, who were already known to Britain's counter- intelligence agency, the Security Service.

Home Secretary Theresa May joined Carlile on Sunday to argue on the BBC that the bill should be revived. "I have always been clear that access to communications data is essential for law enforcement agencies and the intelligence agencies," May said in an interview on The Andrew Marr Show. "Law enforcement agencies, the intelligence agencies need access to communications data and that is essential to them doing their job," she said.

May is a member of the dominant party in the Coalition, the Conservatives, and it's no real surprise her call has been supported by other members of that party, too. But at least some of the Labor opposition have started to add their calls for a resuscitation of the bill's provisions, with former Home Secretary Alan Johnson saying on the same broadcast, "We need to get [a new version of the bill] on the statute book before the next general election."

Civil libertarians have been quick to come to Clegg's defense, with pressure group Big Brother Watch arguing that Britain's terrorist trackers already have just the sort of legislative powers, via RIPA, that Carlile and others say they have been denied, and that "factual errors and cheap rhetoric" are clouding the debate in a shocked post-Woolwich nation.

Thus British police "already have the power to find out who a suspected terrorist is talking to," said Big Brother Watch. How they do so -- "from covert human intelligence sources, covert surveillance, directed surveillance or intercept" -- is up to them. If someone were identified as a possible terrorist, local police and agencies can already monitor their online activity, and if the suspects had used some encrypted form of communication, the Communications Data Bill would "not have yielded any information," claimed the group.