Ontario will slash the number of government agencies and end duplication in the public sector as it struggles to eliminate the deficit in three years.

These plans were laid out Thursday in Premier Kathleen Wynne's mandate letter to Deputy Premier Deb Matthews, who is directing the government's budget-cutting efforts.

"You will…transform and modernize public sector service delivery while protecting vital public services," Ms. Wynne wrote. "You will drive efficiencies and reduce costs to achieve our commitment to eliminate the deficit by 2017-18."

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The instructions came the same day a Conference Board of Canada report warned the province must make even more cuts than it is currently planning if it is to eliminate the deficit on time. The report estimated future government revenues will be lower than Finance Minister Charles Sousa is projecting.

Ms. Wynne released all 30 mandate letters she has written her ministers. The missives are effectively marching orders that detail what the Premier expects each minister to work on during their tenure.

Ontario premiers have used such letters since at least the early 1990s, but this is the first time they have been released publicly.

"I want people to know their government is working for them, but I also want people to know what their government is doing," Ms. Wynne said following a cabinet meeting in Sudbury, Ont., where she distributed the letters. "I want people to know that the plan we ran on [in the spring election] is reflected in the missions I've now given to our ministers."

Most of Ms. Wynne's instructions were previously announced in the 2014 budget – if not earlier – but the letters are meant to itemize them in more straightforward way.

Ms. Matthews and Finance Minister Charles Sousa will likely have the toughest jobs, trying to hold the line on spending while simultaneously revving up the economy with infrastructure spending.

Among other things, Ms. Matthews is expected to cut the number of agencies by 30 per cent compared to 2011 levels. Agencies range from regulatory boards, such as the Alcohol and Gaming Commission, to service providers, such as Legal Aid and the Human Rights Legal Support Centre.

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She is also tasked with reforming the government's information technology system to digitize more of the bureaucracy's operations, hold the line on wage hikes in union negotiations and implement more of economist Don Drummond's cost-cutting recommendations.

The government last year had to burn through a contingency fund Mr. Sousa built into the budget because tax revenues came in lower than expected.

And the Conference Board warns future revenues will also likely not match projections. The Conference Board, for instance, estimates economic growth in 2017-18 will be 0.6 per cent lower than the government does, and the province will run a deficit that year of $2.4-billion instead of reaching balance. To compensate for the lower revenue, the board says, the province will have to constrain health, education and other spending even more than it is now.

Despite this warning, the government is not planning to change its revenue projections. Mr. Sousa's spokeswoman said its estimates are already conservative enough as it is.

"When we make our projections, we consult private sector economists and take a slightly more cautious view as we move forward in crafting the provinces fiscal framework," Susie Heath wrote in an email.

In addition to chopping spending, the government has jacked up income taxes on people making over $150,000 per year. It is also considering whether to sell off part of electricity agencies or the LCBO.

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The letters contained few surprises. But they did outline some policy areas that have received little attention in recent months, including the government's plans for dealing with climate change.

In her directions to Environment Minister Glen Murray, Ms. Wynne orders him to figure out how to reach the province's target of cutting greenhouse gas emissions to 15 per cent below 1990 levels by 2020. In a report this summer, provincial environment commissioner Gord Miller warned the province will miss that target if it doesn't cut down on emissions from transportation.

The note to Mr. Murray also orders him to listen to craft a climate change strategy that will guide the province until 2050.