Justin Trudeau says there's a way for Finance Minister Joe Oliver to save millions in the upcoming federal budget: slash spending on advertising.

The Liberal Leader responded in writing Wednesday to Mr. Oliver's request for low-cost budget ideas. Mr. Trudeau's letter calls on the government to support a Liberal private member's bill that would empower the Auditor-General's office to reject government ads that are considered partisan. The bill would also ban government ads than include the name, voice or image of a federal politician. A similar law currently governs advertising by the Ontario government.

Mr. Trudeau's letter argues that recent government-funded ads are nearly indistinguishable from Conservative Party of Canada advertising.

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"This is a blatantly improper use of public money and is unacceptable to Canadian taxpayers," writes Mr. Trudeau.

Treasury Board records show the government has approved $60.4-million in advertising during the first half of the current fiscal year. Official end-of-year figures are released months after the fact. The most recent records from Public Works are for the 2012-13 fiscal year, when Ottawa spent $69-million on advertising. That was down from a high of $136.3-million in 2009-10.

This year's ad campaigns include $14.5-million on Economic Action Plan and skills training ads, $9-million on Veterans Affairs services and Remembrance Day ads, $7.2-million to promote Canada's 150th anniversary in 2017, $6.5-million on consumer initiatives, $6-million to promote tax measures and $5.5-million on an ads urging young Canadians not to use marijuana or abuse prescription drugs.

The Conservative Party also pays for partisan advertising that addresses some of the same themes as the taxpayer-funded ads, such as the government's economic measures or the dangers of marijuana, which Mr. Trudeau is promising to make legal.

The Liberal Leader's letter also states that the roughly $2-billion annual cost of allowing families with children under 18 to split their income for tax purposes should be scrapped in favour of new spending, in areas like education and infrastructure. Mr. Oliver's original letter had said he would not entertain "reckless" spending proposals from the opposition, but Mr. Trudeau countered that the term describes the government's main announcement this fall.

"Income splitting is not a wise investment, and is, frankly, the definition of 'reckless,'" he wrote. "Rather than implementing unfair tax breaks for the wealthy, we should instead be investing the surplus in areas that will benefit all Canadians, both now and in the long-term."

The income splitting measure announced by Prime Minister Stephen Harper in October will provide up to $2,000 in tax breaks for qualifying families. Supporters say it helps an unfairness in the tax system in which family units are taxed at different rates when one spouse is in a higher tax bracket than the other spouse. However, critics have pointed to independent analysis showing that about 85 per cent of Canadian households would not benefit from the break. The government also announced an enhancement to the Universal Child Care Benefit and child care tax deductions that are available to all parents with children under 18.

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Mr. Trudeau's letter was sent on the same day that the Liberal Party released a new radio ad in which the Liberal Leader voices his opposition to the government's income-splitting policy.

Mr. Oliver had written to NDP Leader Thomas Mulcair and Mr. Trudeau late last month requesting "low-cost or cost-neutral" suggestions for the 2015 budget. Mr. Oliver also wrote that he would welcome suggestions to eliminate ineffective spending in government.

Mr. Oliver responded Wednesday by stating that Mr. Trudeau's letter amounts to a clear pledge to raise taxes by reversing Conservative tax cuts.

"Our Conservative government has offered unprecedented benefits and tax relief for hard-working Canadian families to enable them to have more resources for priorities like child-care and sports and saving for university," said the finance minister in a statement provided by his office. "In contrast, the Justin Trudeau Liberals are explicitly promising to raise taxes across Canada for hard-working families with children."

Mr. Oliver's statement did not address other aspects of Mr. Trudeau's letter, such as the call to reduce and reform ad spending.

A spokesperson for the NDP said the party has not yet responded to Mr. Oliver's letter but will do so in the coming weeks.