The Liberal government is spending only 70 per cent, at most, of what's needed to fulfil its promise to end boil water advisories on First Nations Reserves within five years, according to a new report from the parliamentary budget officer.

Thursday's report says Ottawa will need to invest a minimum of $3.2 billion in capital investment to bring First Nations water systems up to the standards of comparable non-Indigenous communities in order to eliminate boil-water advisories.

It estimates it will take $1.8 billion to estimate the drinking water systems and another $1.4 billion will be needed for wastewater treatment, with an annual operating and maintenance costs of $361 million. Of that, $218 million would be for drinking water alone.

Their analysis says historical spending combined with the nearly $2 billion earmarked still leaves a funding gap. Researchers ran various scenarios using those investments and found funding only covers between 50 and 70 per cent of the total investments needed.

"The recommended capital and operations and maintenance costs are considerably more than the actual and planned funding for First Nations water and wastewater infrastructure," reads the report.

"Obviously, we will study his numbers in detail," said Indigenous Services Minister Jane Philpott.

"Our commitment is firm, and Canadians need to understand that we're absolutely steadfast in our commitment to make sure that all long-term drinking water advisories in public systems on reserve will be lifted by March of 2021. We will make sure that we have the resources to do so and we have a very specific plan in place to get there."

So far, the number of long-term advisories on systems supported by Indigenous Affairs has dropped by just seven — from 77 to 70 — as of the end of July.

'Red flags'

The PBO report comes after a request from Timmins–James Bay MP Charlie Angus.

"This report raises many red flags. The prime minister made a firm commitment to end long-term drinking water advisories on reserve. It's clear he hasn't allocated the funds to keep this promise," said Angus, the NDP's critic for Indigenous youth issues.

"In particular, the chronic underfunding of operations and maintenance will cause more long-term problems for existing water and sewage facilities. Access to clean water is a fundamental right. It is time the government got serious about this."

The Liberal government promised to end long-term boil water advisories on reserves within five years by investing an additional $1.8 billion over five years, starting in 2016-17.

The report also notes that while the government financially supports most systems on reserve, it does not support all systems.

"As such, even if the federal commitment is fulfilled, there may remain inadequate infrastructure as described in subsequent sections," says the report.

The report cautions that its estimates are sensitive to assumptions about population growth and other demographic factors, as well as a variety of capital investment options.

First Nations reserves own the water and wastewater assets on their respective reserves and the federal government is responsible for ensuring safe drinking water on most reserve