HELENA — Two pro-business groups, including one accused of illegally hiding its campaign donors and expenditures in Montana, sued the state Monday, seeking to invalidate a broad range of state campaign-finance laws.

Western Tradition Partnership (WTP) and the Montana Citizens for Right to Work, both of which sometimes mail material attacking legislative candidates shortly before elections, said the suit challenges laws that impose "onerous and constitutional burdens upon (those) engaged in political speech."

The lengthy suit, filed in state District Court at Helena, not only sought to exempt the two groups from the laws and further investigation by the state, but also said the Office of Political Practices' entire investigative process is unconstitutional.

"The time has come for the Office of Political Practices to be cleaned up and reformed," said Donald Ferguson, executive director of WTP. "That starts by stopping (Political Practices Commissioner Dennis) Unsworth's abusive tactics and violations of constitutional rights."

Unsworth ruled Oct. 21 that the Denver-based WTP is a political committee and had violated state law by failing to report campaign-related spending or its donors.

"Instead of standing up and identifying their secret donors, or challenging the findings against them with facts, they choose to attack the law itself," Unsworth said Monday.

He added that Montanans have the right, under their laws, to know who is financing political speech, "and I intend to enforce (those laws)."

WTP, which describes itself as a "grassroots lobbying organization dedicated to fighting environmental extremism" and promoting natural-resource development, and the Right to Work group, which says it's fighting "compulsory unionism," are challenging many of those laws as unconstitutional.

In either the 2008 and 2010 elections in Montana, both groups have sent questionnaires to state legislative candidates, asking about issues important to the groups.

If the candidates fail to answer the questionnaire or give answers contrary to the groups' position, the groups sometimes then mail material to voters shortly before the election, attacking the candidate for his or her actions related to the questionnaire. The mailers often mention the candidate's opponent as having filled out the questionnaire in favor of the groups' positions.

The two groups maintain these mailers are educational and are not meant to influence the outcome of elections.

The lawsuit filed Monday said this "issue advocacy" communication is not subject to Montana's political committee laws, and that the laws themselves are unconstitutionally vague.

The state laws that says an expenditure can be regulated if it's "for the purpose of influencing the results of an election" is "impermissibly vague and overbroad," the lawsuit said.

The suit also asked a state judge to invalidate Montana's law prohibiting corporations from making "in-kind" donations to help candidates; to throw out a law requiring groups to identify themselves on political mailers; and to block further investigation by Unsworth of other complaints filed against WTP.

WTP even asked the judge to forbid Unsworth from publicly distributing his Oct. 21 decision against the group, saying it is causing the group "irreparable harm to its mission and reputation" with "unsubstantiated allegations" and by revealing its internal communications and fund-raising strategies.

The suit also said Unsworth's investigatory process violates constitutional rights because it doesn't give the target a chance to for a hearing or to cross-examine witnesses before a ruling is issued.

HELENA — A conservative group has filed a lawsuit in its fight against charges that it illegally hid work to influence elections.

Western Tradition Partnership was the group also behind the lawsuit that lifted Montana's century-old ban on corporate political money.

The Montana Commissioner of Political Practices filed a lengthy complaint last month against the group.

The ethics chief argued the group violated campaign finance law numerous times by failing to disclose money spent on pieces attacking candidates for office.

Western Tradition Partnership and another group countered Monday in the new lawsuit that the commissioner's investigation oversteps its legal boundaries and violates WTP's constitutional rights.