A military police watchdog agency has subpoenaed senior federal officials and filed a court application to force the Conservative government to release information about the transfer of suspected Taliban fighters to Afghan custody.

The Military Police Complaints Commission is trying to get around what it considers roadblocks in its investigation of allegations that the Canadian military handed over prisoners knowing they would probably be tortured.

Sylvain Roy, chief of staff to the commission chair, says the application to the Federal Court involves redacted documents already released to the inquiry.

Deputy foreign affairs minister subpoenaed

Investigators believe the records have been overly censored.

He says subpoenas have been served on four former commanders of Canadian troops in Kandahar, the deputy minister of foreign affairs, four foreign affairs employees and the chief of the Correctional Service of Canada.

Roy would not explain how many of the subpoenas are aimed at uncovering documents and which are intended to summon the officials as witnesses in the commission's planned public hearings.

He would only say they are relying on the "co-operation of the parties."

Federal lawyers have challenged the validity of the commission to hold such public-interest hearings into the 2007 complaint by Amnesty International and the B.C. Civil Liberties Association.

In its attempt to derail the commission inquiry, the federal government has argued that the handling of prisoners is "not subject" to oversight by the military police complaints process.

Ottawa also argues that the National Defence Act only gives the agency the power to investigate conduct complaints related to military police.