Conservative senators are throwing in the towel over a planned investigation into the failed prosecution of Vice-Admiral Mark Norman.

The deputy chair, Senator Jean-Guy Dagenais, signalled in a letter on Sunday that he intends to withdraw his motion and ask instead for a public meeting of the National Security and Defence committee to formally discuss the issue.

Norman, a career naval officer, was accused of leaking cabinet secrets related to a $668-million shipbuilding deal, but the Crown stayed the charge after the defence presented new evidence, including statements from witnesses the RCMP had never interviewed.

CBC News reported in May that new information included the revelation that Norman not only had the blessing of the former Conservative cabinet to deal with the Davie shipyard, he was authorized to speak with it directly in the run-up to the signing of the leasing contract.

A copy of Dagenais's letter sent to the committee chair, independent Senator Gwen Boniface, was obtained by CBC News.

Running out of time to investigate

In the note, Dagenais said, in order hold hearings beyond the Senate's scheduled adjournment on June 20, there needed to be agreement from both the government and opposition.

He said it became clear, following a meeting on Thursday with independent Senator Peter Harder, the government representative in the Upper Chamber, that there would be no such permission.

The Liberals "literally want to prevent the truth from coming out in this political scandal," Dagenais wrote.

A handful of independent senators sided with the Conservatives at the end of May to investigate how the criminal case against military's former second-in-command, who was charged with one count of breach of trust, collapsed earlier this spring.

House declines to investigate

The Liberal government was accused by Norman's lawyers and the Opposition of political interference throughout the lengthy pretrial process — something both senior cabinet ministers and the public prosecution service denied.

The House of Commons defence committee declined to investigate the circumstances and the policy issues which led to Norman, the former commander of the navy, being charged.

Dagenais wanted the Senate to call Norman, his boss Gen. Jonathan Vance and Defence Minister Harjit Sajjan to answer questions.

He drew up a list of 10 names for hearings that could have lasted up to five days. But he accused Liberal senators and others in charge of issuing the witness invitations of delaying in order to run out the clock on the sitting.

Vows to keep issue in public eye

Dagenais described it as blatant "manipulation." He said he hopes "the suspicious and questionable suspension of Vice Admiral Norman will remain" in the public eye and that the public and the media will continue to demand answers.

CBC News asked Boniface and Harder for comment, but neither was immediately available Sunday afternoon to respond.

After being suspended and removed from his job as vice chief of the defence staff, Norman has been welcomed back and indicated he wants to continue serving.

His job is currently occupied by another officer and it's unclear what post he could assume.

Last week, he attended the navy change of command in Halifax where his presence was acknowledged by both Vance and a warm round of applause by the sailors in attendance.