(ABC News) — Democratic presidential candidate Bernie Sanders’ campaign is accusing his rival Hillary Clinton and the Democratic National Convention (DNC) of “serious apparent violations of campaign finance laws” by improperly allocating money obtained through joint fundraising.

In a statement released Monday, the Sanders’ campaign wrote that the joint fundraising committee Hillary Victory Fund (HVF) is being “exploited” to solely benefit Clinton’s campaign for president.

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In joint fundraising, the Federal Election Commission (FEC) allows two or more political committees (in the case of HVF, the DNC and Hillary for America) to fundraise together. These agreements are not uncommon and allow the two parties to split the cost of hosting the fundraiser and sharing the proceeds. Sanders also signed a joint fundraiser agreement with the DNC in 2015.

FEC rules states that the two participants should divide the money raised from a fundraiser based on an “agreed upon allocation formula.” But if the allocation formula results in an “excessive contribution” for either party involved, the excessive portion has to be split among the other participants.

“It is of grave concern that the Clinton joint fundraising committee appears to be using funds raised by ‘big dollar’ donors to fund activities that yield contributions and support that only provide benefit only to HFA,” Brad Deutsch, the attorney for Sanders’ campaign, wrote in a letter addressed to DNC chair Debbie Wasserman Schultz and mailed Monday.

“The letter questioned whether the Clinton presidential campaign violated legal limits on donations by improperly subsidizing Clinton’s campaign bid by paying Clinton staffers with funds from the joint DNC-Clinton committee,” the statement declares regarding the letter sent by Deutsch.

This accusation is in addition to the lawsuit the Sanders campaign filed in March against the DNC over access to voter data files.

Clinton’s campaign manager, Robby Mook, argued that the Sanders’ campaign is “resorting to baseless accusations” and called the move “shameful.”

“The Sanders campaign’s false attacks have gotten out of hand,” Mook said in a statement released Monday in response to the accusations. “As Senator Sanders faces nearly insurmountable odds, he is resorting to baseless accusations of illegal actions and poisoning the well for Democratic candidates up and down the ticket. It is shameful that Senator Sanders has resorted to irresponsible and misleading attacks just to raise money for himself.”

The statement continued: “Furthermore, we call on Senator Sanders to end his frivolous and cynical lawsuit against the DNC….”

Mark Paustenbach, national press secretary for the DNC, responded to the campaign’s accusations Monday, saying: “The DNC offered to engage in the same joint fundraising efforts with all the major presidential candidates early in the cycle and we welcome the efforts of the candidates to help raise money for the DNC and state parties now to ensure we can build out the infrastructure to win in November.”

According to the DNC, the Sanders campaign could use the joint fundraising agreement to their benefit. The organization argued that the Clinton campaign paid a proportional part of the cost all fundraisers and that it is not subsidizing the Clinton fundraising effort.

ABC’s MaryAlice Parks and Liz Kreutz contributed to this report.