The Wildrose party says the signs, in hues similar to Tory colours and featuring Premier Allison Redford's name, are nothing more than partisan political advertising.
Documents obtained by the Canadian Taxpayers Federation show the government put up 293 blue-and-orange "Building Alberta" signs in 2013.
The material obtained through an access-to-information request shows the average cost was $3,500 per sign.
The signs announce roads, bridges, schools and other infrastructure the government is paying for.
Christine Way with the Transportation Department says every infrastructure project involving provincial money got a sign and the total number of signs is high because of all the rebuilding after devastating floods in June.
She said the colours conform with the province's official branding and added that including Redford's name is in line with past practice.
"These signs often include the names of elected officials and in this case the name of our premier," Way said Thursday. "These signs are about ensuring Albertans know about how their tax dollars are being spent and it is no surprise that the Opposition is trying to make this about the premier.
"As usual, they are way off the mark on this."
In November, the Wildrose released an email from a senior official in the premier's office who instructed ministers to make sure the signs were "up and in front of every flood-affected road, bridge, school ... literally everything on our infrastructure list."
The email told ministers to get the signs out quickly and regardless of cost.
"This was never about informing Albertans about anything meaningful," Wildrose finance critic Rob Anderson said in a release Thursday. "It was about boosting the premier's image at taxpayers' expense.
"The premier needs to apologize for this partisan use of tax dollars, immediately cancel this politically motivated campaign and order her party to pay back the money."
Anderson also said that "binge spending" on signs is "disgraceful" at a time when the government is cutting programs and funding.
"One million dollars could have done some real good by funding 20 new teachers, or over 30 hip replacement surgeries."
The Wildrose have needled the government for months over the signs. In one tongue-in-cheek publicity stunt, the party put up its own signs at the legislature to mock the Tories.
Signs in the building's washrooms reminded users that Redford was also "building Alberta" by replacing urinal pucks and buying toilet paper. Others reminded staff that putting up Christmas lights, replacing lightbulbs, moving dirt and shovelling snow were also acts of building the province.
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