Charlie Angus, the party's access to information and ethics critic, also wants information commissioner Suzanne Legault to look into whether other federal agencies are doing the same thing.
The Toronto Star reported last month that the federal revenue agency had destroyed all text message records of its employees and stopped electronically saving such messages.
The newspaper cited documents released under the Access to Information Act that said Shared Services Canada — the federal organization responsible for information technology services — had wiped the records last August.
The revenue agency told the Star it considered the messages transitory, and had instructed the computer services organization to destroy them and to stop logging its employees' instant messages, including regular texts, BlackBerry messages and PINs.
In Monday's letter to Legault, Angus said the agency did not verify whether it had a process to determine if any of the records were of business value, in which case they should have been preserved and made accessible to requesters under the access law.
The letter said the mass deletion of records raises "serious questions" about what is being hidden from Canadians at a time when the revenue agency is closely auditing the activities of many left-leaning and environmental charities — audits some say are intended to chill critics of Conservative government policy.
The public has a right to know who is directing the audits and for what reasons, Angus said in an interview. But the use of instant messaging — and the regular disposal of those messages — means such communication won't be part of the accessible government record.
"Whenever I talk to anybody in the public service now, they tell me political directives are passed on through this parallel track of electronic communication — the PINs and these other forms of communication," Angus said.
Neither the revenue agency nor Legault's office had immediate comment on Angus' complaint.
In a November 2013 report, Legault recommended a virtual ban on instant messaging with federally issued BlackBerrys and other wireless devices because the texts evaporate so quickly.
Legault said instant messages were automatically deleted — usually after 30 days — meaning Canadians couldn't request them under the Access to Information Act.
"If instant messages, including PINs, were treated in the government of Canada in the same manner as emails, many of the concerns about the impact of instant messaging on access would be addressed," Legault said in her report.
"Instead, instant messages, for the most part, are not backed up on servers, are automatically deleted after a set period of time and are, as a result, not recoverable."
Legault recommended disabling instant messaging on government wireless devices, except when there is a genuine operational need for it and measures are taken to archive such messages on a federal server "for a reasonable period of time."
Treasury Board President Tony Clement rejected the idea of disabling instant messaging, instead agreeing to direct public servants to preserve such messages, "for example by being forwarded into the email system."
In his letter to Legault, Angus said Clement's commitment now appears to be hollow.
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