Beware. The state of Massachusetts may come looking for the federal government to bail it out of its financial mess. Recent cost increases coupled with past mismanagement and corruption during construction of Boston’s Central Artery/Tunnel project (Big Dig), the most expensive highway project ever planned in the U.S., could drive the state to seek additional federal help.

Total costs for the 7.5 mile urban highway, bridge and tunnel project have now increased to $11.6 billion. Furthermore, the state’s plan to pay its share is inadequate, according to a recent report by the U.S. General Accounting Office (GAO). Federal taxpayers must say “no” if the state asks for more money. After all state officials promised to contain costs and avoid additional federal help.

When federal funding for the Big Dig was originally allocated in 1991, Senator Edward Kennedy (D-MA) promised that Massachusetts would not seek additional federal help.

But project costs have continued to spiral, quadrupling from the original $2.5 billion cost estimate and overwhelming the $10.4 billion figure that state transportation officials repeatedly swore costs would not rise above.

Federal taxpayers are already on the hook for $4.7 billion of the $5.7 billion currently obligated for the project. Financing the almost $6 billion remaining will be tricky. The state’s financing mechanisms for its share come up short, according to both the GAO and the Massachusetts Taxpayer Foundation — even if the state’s novel financing plan is accepted by financiers. The state, in a scheme that the GAO argues is problematic, hopes to borrow money against future federal funds that may not even be authorized until 2003.

This means that the state needs money — but raising taxes in a high-tax state is difficult and state borrowing is unlikely. Massachusetts already has one of the highest debt burdens in the nation and has put measures in place, such as limits on the issuance of new debt in order to improve its credit rating, according to the GAO.

Further compounding the state’s financial difficulties is the upcoming reauthorization of the federal transportation law under which Massachusetts is likely to receive less funding. This funding reduction will likely aggravate intrastate transportation funding squabbles because the Big Dig currently gobbles up about 70 percent of the state’s federal highway money. Taxpayers must not allow special earmarked funds to bail Massachusetts out of its own problem.