The infrastructure department has had $1.75m a week to spend on ads spruiking the government’s policies in the final six weeks before the election is called.

According to the department, $9m of the budgeted $20m for the Building Our Future campaign was spent before 28 February, leaving $11m to be spent from the start of March until 13 April. That equates to at least $250,000 a day for the infrastructure campaign.

The campaign is promoting the Coalition’s 10-year $75bn infrastructure package in the 2018 budget, of which $24.5bn was for new projects and just $4.2bn of that was due to be spent in the first four years.

After the budget on Tuesday, the government is expected to call the election for 11 or 18 May, implying it will be called by 13 April at the latest.

The infrastructure department said the campaign “is scheduled to run until 13 April 2019 but not all funds must be spent”. Although $20m was allocated to the campaign the department said it plans to spend $17.6m.

Other big spending government advertising campaigns include:

$18.7m for the treasury’s Better Tax campaign about the Coalition’s income tax changes made in 2018

$9.4m for the education department’s Quality Schools campaign for changes to school funding made by the Turnbull and Morrison governments

$8.1m for the environment and energy department’s Powering Forward campaign, which helps consumers seek the cheapest offer from their energy provider

Those departments did not clarify how much was left in their campaign war chests. The environment department said its campaign was “still under way” and Treasury confirmed its campaign was “still active”.

AusTender documents show that cumulatively the government has committed more than $200m to advertising since 1 January 2018.

In January the prime minister, Scott Morrison, argued taxpayer-funded ad campaigns were “entirely appropriate for Australians to understand what their government is doing”.

He praised the infrastructure campaign in particular, saying it explained that “what we’re doing is delivering record spending on delivering major infrastructure projects, congestion busting around Australia”.

The shadow treasurer, Chris Bowen, said the increasing use of millions of taxpayers dollars on “partisan government advertising” was a sign of “desperation”.

The Greens’ democracy spokeswoman, Larissa Waters, said: “Taxpayers shouldn’t be footing the bill for the government’s propaganda campaigns just months out from a federal election.”