WASHINGTON — Even the federal government turns to private shippers rather than the Postal Service when it wants to send packages.

A report from the agency’s inspector general said that since 2001, private companies like FedEx and United Parcel Service had consistently captured 98 percent of the revenue from long-term shipping contracts with the government because the financially troubled Postal Service did not have a sales staff or a strategy to focus on the federal sector until 2009.

The report said the Postal Service lost out on about $34 million in potential revenue over the last two years, a relatively small amount for an agency that reported $65 billion in revenue last year. But officials at the inspector general’s office said the Postal Service, which had a net loss of $15.9 billion last year, could not afford to pass up opportunities to generate revenues and profits no matter how small.

“Every little bit helps,” said Agapi Doulaveris, a spokeswoman for the inspector general’s office. “The purpose of our audits are to help them identify ways to do things better. Every opportunity we identify helps adds to their bottom line.”