With the fate of the Liberal government’s security bill in doubt, the historically secretive Canadian Security Intelligence Service is laying its cards on the table and arguing its investigations will suffer if changes aren't made.

Senior CSIS officials, speaking on the condition they not be named because of the nature of their job, said the agency is struggling to get court-approved information from electronic service providers, making it harder to investigate national security cases.

“If Canadians understood they would be increasingly worried,” said one source.

The comments from the service were raised in a recent briefing with CBC News about Bill C-2, the Liberal government’s controversial bill that has been roundly — and loudly — criticized by civil liberty and privacy groups .

CBC News requested the briefing to better understand the intelligence agency’s challenges and hear what it told the federal government before the bill — one of the first pieces of legislation tabled by Prime Minister Mark Carney’s government — was crafted.

The omnibus bill was initially introduced as legislation meant to bolster border security, but it also included lawful access and surveillance changes for CSIS and the RCMP.

The National Security and Intelligence Committee of Parliamentarians published a report this year calling for changes to how organizations like CSIS can legally access Canadians' cellphone da