Private groups spent $5.8 million to send Congress members on some 1,600 trips last year, according to data gathered by LegiStorm.

This tab – 75% up from the year before – is the largest amount since ethics reforms were enacted in 2007 in the wake of the Jack Abramoff scandal.

While lobbyist are banned from sending Congress members on trips, groups that don't lobby can legally sponsor educational and informative trips. But the motives of these organizations may be questionable as many former lobbyists and other people with interests often serve on their boards.

Here are some of the findings by LegiStorm about privately-funded Congressional travel in 2011:

• 555 trips (out of 1,600) were international.

• The average international trip cost $8,595.

• Overall, the average trip lasted more than four days and cost $3,638.

• The travel sponsor with the deepest pockets in 2011 was the American Israel Education Foundation, which paid more than $2 million for 145 trips to Israel.

• The seven most-traveled members of Congress in 2011 were all Democrats, led by Rep. Jim McDermott (D-Wash.) who took 10 trips. Rep. John Lewis (D-Ga.) was second, with nine.

• Rep. Jim Cooper (D-Tenn.) was the biggest spender, taking six trips worth $47,035, including an Aspen Institute trip to Barcelona in September worth more than $18,000.

• The most expensive trip was sponsored by the International Conservation Caucus Foundation, which paid $30,708 to send Rep. John Carter (R-Texas) and his wife to South Africa and Botswana.

Watch below the report by CBS for more: