Americans for Tax Prosperity, the free-market political nonprofit associated with the Koch brothers, began what it described as the first wave of its planned activism for tax reform with an ad campaign urging Republicans to support lower tax rates and a simpler system.

The group said that it will spend several hundred thousand dollars on web and social media ads targeted to sympathetic readers in the districts of a handful of key House Republicans.

The ads will tell the readers to ask their representatives to "support AFP's plan to un-rig the economy." The ads will redirect to a signup form for a petition for tax reform.

The group's principles for tax reform include lower rates, a simpler system, greater fairness and no new tax burdens, such as a carbon tax or value-added tax.

Also discouraged is the border-adjusted corporate tax introduced by House Republicans, including Speaker Paul Ryan. In recent months, Americans for Prosperity has lobbied hard against that provision, which would effectively place a tax on imported goods, hitting refineries such as those owned by Koch Industries. The group has mounted a relentless public relations campaign against the idea of the border adjustment, circulating statistics portraying the idea as a major tax increase on consumers.

Yet the group favors tax reform, without that specific provision.

Among the lawmakers initially targeted are members of the tax-writing Ways and Means Committee, including Reps. Kevin Brady of Texas, Peter Roskam of Illinois, Carlos Curbelo of Florida, Jackie Walorski of Indiana, Diane Black of Tennessee, Lynn Jenkins of Kansas, George Holding of North Carolina and Kristi Noem of South Dakota.

Americans for Prosperity says it plans further activism, including grassroots action and events, as congressional Republicans work on tax legislation.