Malcolm Rifkind, chairman of parliament's Intelligence and Security Committee which oversees the work of Britain's spy agencies, said their staff had "noble motivations" and no desire to be "all-seeing" or "all-hearing".
Britain's security agencies, like their U.S counterparts, have faced great scrutiny since Snowden, a former contractor with the U.S. National Security Agency (NSA), disclosed details of their work to newspapers.
Snowden caused an international uproar last June when he leaked documents revealing the extent of surveillance and electronic intelligence gathering by his former employers and by their British equivalent, GCHQ.
"Unfortunately, the insidious use of language such as 'mass surveillance' and 'Orwellian' by many of Mr Snowden's supporters to describe the actions of Western agencies blurs, unforgivably, the distinction between a system that uses the state to protect the people, and one that uses the state to protect itself against the people," Rifkind said.
"It is ironic that Mr Snowden, in the name of privacy and the rule of law, chose China and Russia from which to launch his attack on the United States," he said in a lecture at Oxford University.
"GREATER DEGREE OF INTRUSION"
In the wake of his leaks, Snowden fled the United States, where he faces espionage charges, and has since been granted temporary asylum in Russia.
Civil liberties groups, parts of the media and lawmakers from all parties have argued that Snowden's disclosures about the scale of government monitoring show it needs to be reined in and security agencies put under greater oversight.
But British spy chiefs say Snowden leaks have put operations at risk. Last week, a senior security official said data showed terrorists had substantially changed their methods of communication because of the leaks.
Rifkind has been a staunch supporter of the intelligence agencies since the Snowden disclosures were made. Last July, his committee cleared GCHQ of allegations its spies had circumvented the law by using data gathered by a clandestine U.S. programme.
He said the communication over the internet meant there was likely "to be a considerably greater degree of intrusion into the privacy of the public by the security services", which left some anxious they were conducting general surveillance.
"Our agencies are not, and do not wish to be, 'all-seeing' nor 'all-hearing'. Their capabilities have been designed to pursue their lawful, narrowly defined objectives," said Rifkind.
"True public servants operate with noble motivations, lawful authority and (are) subject to rigorous oversight. That is how those who work for our intelligence agencies see themselves. That is how most of the public see them."