A government watchdog group called for an investigation Thursday of House lawmakers who bunk nightly in their Congressional offices, asserting the Members are violating House rules and tax laws.

In a letter to the Office of Congressional Ethics, Citizens for Responsibility and Ethics in Washington Executive Director Melanie Sloan alleged that lawmakers who regularly sleep in their offices are “misusing official resources.”

“Members who sleep in House office buildings appear to violate House rules,” Sloan wrote. “The Member Representational Allowance may only be used for official and representational expenses, it may not be used for personal expenses.”

The letter identifies nearly three dozen Members who have been cited in media reports as using their offices as a home while on Capitol Hill.

According to Sloan’s letter, Members’ use of their offices as a makeshift bedroom could violate House rules that limit lawmaker’s personal use of official equipment and supplies.

“Routinely using House facilities in this manner can hardly be considered ‘incidental personal use,’” Sloan wrote.

Sloan also asserts that Members who sleep in their offices must claim the benefit on tax forms, comparing it to the parking benefit Members and staff must declare on their annual income tax forms if they utilize one of the House parking garages.

“If parking is a taxable fringe benefit, then surely, so is lodging,” Sloan wrote. “At the very least members of Congress who sleep in House office buildings should have the fair market value of their housing — anywhere from $1,500 to $2,000 a month — attributed to them as imputed taxable income”

According to a Congressional Research Service report on Member salaries, lawmakers are permitted a special tax deduction of up to $3,000 annually for living expenses away from their Congressional district or home state.

The OCE reviews potential rules violations and issues recommendations to the House Ethics Committee. Only the Ethics Committee can determine whether a Member violated the chamber’s rules and decide whether a lawmaker should be punished.