ST. PAUL — A Minnesota campaign finance oversight board is weighing whether to impose new fees on lobbyists, candidates and political parties to address budget strains that have been exacerbated by added calls for investigations.

The fees discussed Monday are being developed by the Minnesota Campaign Finance and Public Disclosure Board as a backup plan if lawmakers balk a request for increased funding from the state’s general treasury. Board members and staff acknowledged that required annual fees could face free-speech court challenges or discourage political participation.

Campaign board executive director Gary Goldsmith said a multi-year budget pinch has left the watchdog agency in an untenable place. It has fewer staff than ever even as complaints leading to investigations have increased. In 2012, the board launched 31 investigations — nine are still open — compared with the 34 probes it undertook from the previous five years combined.

“I’m not kidding anymore that we cannot do everything we are doing,” Goldsmith said in presenting a budget recommendation that will be formally acted upon Wednesday.