ST. PAUL, Minn. – AT&T's lobbying strategy at this summer's Democratic and Republican conventions? More bars in more places.

The Dallas-based telecommunications giant has been a larger-than-life presence at both political conventions, hosting dozens of top-dollar delegation parties and star-studded soirees.

Senior AT&T officials say they're at the conventions to showcase the company's role as a good corporate citizen – and to show off their top-of-the-line technology.

"The presidential conventions give AT&T a unique opportunity to present and display the many leading-edge technologies and innovations that we offer," said Michael Balmoris, a spokesman for the company's legislative arm.

But watchdogs say the posh parties are just another way for big corporations to improperly influence state and national leaders. While AT&T is one of the worst offenders, these opponents say, they're one of many.

"They throw these lavish events so that, when everybody returns to Washington or their home state, [the lobbyists'] phone calls get returned," said Nancy Watzman, whose Party Time project tracks corporate spending at the political conventions.

Ethics rules adopted by Congress prevent corporations or lobbyists from throwing parties for individual members, though they may host events to salute certain groups.

These parties must be limited to drinks and finger food – no sit-down meals. If big-name musical acts perform, members must pay to attend.

Still, the lines are often blurry.

In Denver, AT&T held daily lunchtime events for state delegations at a luxury club, and co-hosted exclusive parties for the Screen Actors' Guild and for the Blue Dogs, the House's moderate and conservative Democrats. They were one of several sponsors of a Kanye West concert.

In St. Paul, AT&T hosted separate receptions for young, Hispanic and black Republicans, as well as parties for five state delegations – including Texas.

A reporter who arrived at the Texas delegation event, which featured Southwestern cuisine, tiki torches and bars outfitted to look like Old West fences, was turned away at the door.

"There's no way you would've been on the list," said an organizer of the event, which honored Gov. Rick Perry.

In Denver, AT&T was the "official wireless provider."

At both conventions, the company has had iPhones, wireless handsets, digital touch-screen signs and other mobile applications on display.

Since 2005, AT&T executives and employees have contributed more than $7 million to federal candidates, according to the nonpartisan Campaign Finance Institute. They have spent more than $50 million on federal lobbying.

"It's our view that every four years people around the globe are watching the U.S. and how we pick a leader," Mr. Balmoris said.

"AT&T's role as a good corporate citizen is to showcase the elective process in the best light possible."

Staff writer Katie Brindell contributed to this report.