Democratic U.S. Rep. Collin Peterson is pushing back against a Republican ad that blasts him for his office's car leases and the mileage reimbursements he receives for traveling around his district in his personal airplane.

The ad is part of the National Republican Congressional Committee's $300,000-plus campaign to highlight the costs Peterson has accumulated while traveling across his 38-county district.

"Since 1991, I've been out there doing my job, meeting with constituents, and covering more events and meetings than I could if I was using a car," Peterson said in a statement. "Minnesota's Seventh District stretches from the Canadian border almost to the Iowa line. These Washington outsiders have no idea how large and diverse this district is, how much ground it covers, or how to get around within it. Their ignorance is frankly remarkable."

With the campaign arms of the national Democratic and Republican parties pumping millions of dollars in attack ads into Minnesota's Seventh Congressional District race, both Peterson and his Republican opponent, Torrey Westrom, will be fighting back against a bevy of negative advertising . The NRCC has made $2.8 million in requests for ad time to go after Peterson while Democrats have booked $1.5 million for anti-Westrom ads.

The barrage of attack ads illustrates how high the stakes are in the race, where Peterson is seeking a 13th term and Westrom is aggressively pursuing an upset in the Republican-leaning district. GOP presidential nominee Mitt Romney won the district by almost a 10-point margin in 2012, but Peterson -- the top Democrat on the House Agriculture Committee -- has coasted to re-election for much of his tenure in Congress.

Peterson should expect criticism of his travel costs to continue, GOP aides said.

"The last two [ads] have obviously highlighted Collin Peterson's use of taxpayer-funded perks and it's definitely a major theme of this campaign," said NRCC spokesman Tyler Houlton.

After the NRCC aired its first Peterson ad, Democrats struck back with an ad criticizing Westrom for taking his legislative pay during Minnesota's 2011 government shutdown. Westrom was among more than 100 state lawmakers who continued collecting his check.

"This is what desperate Democrats do when they know they are on the verge of losing," Minnesota Republican Party Chair Keith Downey said in a statement this month.