The U.S. lawmakers have invested a total of 195.5 million U.S. dollars in the defense department's contract companies and gained much profit from the Iraq war, said a new study released on Thursday.

The Center for Responsive Politics, a Washington-based nonpartisan group, conducted the study by reviewing lawmakers' financial statements in 2006.

From 2004 to 2006, a total of 151 Congress members invested 78. 7 million dollars to 195.5 million dollars in companies that have contracts with the Pentagon, and brought them profit of between 15. 8 million dollars and 62 million dollars, according to the study.

It also found more congressional Republicans than Democrats have stocks in the defense companies, but Democrats' military- related investment in 2006 is higher than Republicans, which is 3. 7 million dollars to 577,500 dollars.

The Center for Responsive Politics voiced the concerns that lawmakers' investment in the defense department contractors could constitute a conflict of interest as they take part in the decision-making on Iraq war budgets.

The Center's member, Lindsay Renick Mayer, said profiting from companies tied to the military "could be problematic" for members that oversee defense policy and budgeting.

The two Senators and presidential candidates, John McCain and Barack Obama, did not report any investment in the defense-related companies. Another contestant, Hillary Rodham Clinton, did note holdings in such companies as Honeywell, Boeing and Raytheon, but sold the stock in May 2007, the study added.