Washington (CNN) Congressional law enforcement officials want to rein in the growing number of parties in the Capitol during the annual Memorial Day and July Fourth concerts, according to a letter from the U.S. Capitol Police Board that was sent to top congressional leaders this month.

The letter, obtained by CNN, cites security concerns, mounting overtime costs and an abundance of "coolers containing liquids" as prompting the need for action. It says the changes are needed "in light of the current heightened threat environment" and "to reduce the potential for a breach of decorum or conduct that could prove embarrassing to the Congress."

Authorities are concerned the parties, hosted by lawmakers, their staffs and organizers of a nationally televised concert and fireworks display, have grown out of control and potentially dangerous in recent years. During July Fourth celebrations last year the U.S. Capitol was overrun with heavy drinking party-goers. And it wasn't the first time the building was filled with drunken revelers wandering the historic hallways during patriotic celebrations.

Congress isn't in session during these holidays but many members stay in town to attend the concerts and parties.

The letter, from the officials charged with protecting the U.S. Capitol, is a stunning admission of how much the security situation has deteriorated during these events. While there have been no arrests, there have been falls and injuries that were blamed on excessive drinking, according to a congressional source who said there was a near fall from a balcony that could have been catastrophic.

Now authorities have had enough and are trying to crack down.

"The enormous growth in the sheer number of people inside the Capitol on the evening of both concerts has made enforcement of the basic rules of decorum extremely difficult to manage or enforce," the letter states. "It is especially difficult to monitor and enforce restrictions on the House floor, private hallways and leadership and committee offices. Due to the large number of unescorted guests inside the Capitol, it is virtually impossible for Capitol Police to maintain the integrity of all private areas and offices within the building."

The Police Board says increasing costs are another reason to curb activity in the Capitol. Taxpayers paid $735,252 for 12,174 hours of police overtime during "setup, rehearsals and the concerts themselves" last year, the letter says.

The board is recommending two major changes to avoid another free-for-all this summer.

By limiting access to members of Congress and their guests and staffers who have offices in the Capitol building, the board would block most congressional staffers and employees -- who work in the House and Senate office buildings -- from entering the Capitol on the evenings of the two concerts. This would decrease the number of people attending the informal gatherings in in offices, balconies and other places overlooking the West Front grounds.

These parties have built a reputation in recent years as out of control and freewheeling. One congressional source familiar with the situation described the board's efforts as an attempt to take control by reeling the parties back before there is a security threat or someone gets hurt.

"The Upper West Terrace has been open to members, staff and guests for the past several years to view the concerts. What started out as a small accommodation for staff with offices in the Capitol has grown to the point where it is virtually impossible to control and/or limit numbers to achieve safe evacuation levels," the letter says. "The enormous number of attendees inside the Capitol and on the terrace on both Memorial Day and July 4, places undue pressure on the Capitol Police and therefore increases the risk not only to the Capitol but to members, staff, and attendees alike."

Since 9/11, security at the Capitol has increased dramatically, but law enforcement says they are still vulnerable. The $621 million Capitol Visitors' Center was built to screen most guests a few blocks from the Capitol building. Visitors face tight limits on what they can carry in.

But the letter says those restrictions "have been lessened in recent years during the concerts, thus rendering secure access protocols of the building unenforceable."

People who work in the Capitol are allowed to bring in liquids but visitors are not. The letter points out that on the evening of the concerts all bets are off as "numerous guests of staff arrive at the Capitol with bags and coolers containing liquids. These liquids are very frequently sanctioned as 'staff property' and allowed to bypass the regulation to expedite the security screening process."

"Liquids" is a euphemism for alcohol, according to the multiple congressional sources.

The board also wants to move post-concert receptions to the U.S. Botanic Gardens, a glass-encased, greenhouse-type building at the edge of the Capitol grounds. Doing so would mean fewer police officers would be needed to screen guests coming into the Capitol when the concerts end. But that would mean hundreds of wounded service members and veterans would not be able to be honored at the receptions in Statuary Hall, a stately and impressive room adjacent to the Capitol Rotunda that houses life-sized statues of American patriots.

These receptions also include members of Congress, other government dignitaries as well as the entertainers, television producers and corporate sponsors of the concerts.

"The post-concert receptions hosted by the concert organizers have outgrown Statuary Hall," the letter from the Police Board says. "Guests roaming such a large area, encompassing two floors, make it very difficult, if not impossible for the Capitol Police to monitor everyone effectively and thus prevent persons from wandering into restricted areas and private congressional spaces."

The letter says service members will still be granted "the special access and recognition they deserve as the tour the Capitol free of disturbance or distraction."

A congressional source said details are still being worked out as to when those tours will take place.

The March 12 letter was sent to House Speaker John Boehner, House Democratic Leader Nancy Pelosi, Senate Majority Leader Mitch McConnell and Senate Democratic Leader Harry Reid. It was signed by the Frank Larkin, the Senate Sergeant at Arms and chairman of the Police Board; Paul Irving, the House Sergeant at Arms; Steven Ayers, the Architect of the Capitol; and Kim Dine, the chief of the U.S. Capitol Police. The four men make up the U.S. Capitol Police Board, which oversees law enforcement on the sprawling campus.

CNN reached out to the concert organizers, Capitol Concerts, but they did not respond to requests for comment. Former Louisiana Republican Rep. Bob Livingston, who is now a lobbyist and who represents the company, also declined to comment.

The congressional leaders haven't yet approved the access restrictions, but one source familiar with the situation said a decision was expected in the coming weeks.

"We will continue to work with the Capitol Police Board and other leaders on this issue but no decisions have been made," said Kevin Smith, a Boehner spokesman.

In 2007 when House Democratic Leader Nancy Pelosi was speaker, she began the tradition of inviting injured service members to the Capitol events. A spokesman for Pelosi said she "will carefully consider" the board's recommendation.

JUST WATCHED Being Moody: How to drink like an American Replay More Videos ... MUST WATCH Being Moody: How to drink like an American 02:02