The Electoral Commission has said it would like powers to seize documents more quickly during investigations into alleged violations of electoral law.
Officials from the elections watchdog told MPs they were currently able to obtain warrants and search premises and, if needed, seek a court order.
But they said greater "immediacy" was needed when targeting other groups assisting high-profile campaigners. A series of investigations relating to the Brexit referendum are continuing.
Last week, the regulator fined the pro-Brexit campaign group Leave.EU £70,000 for breaking spending rules during the 2016 campaign. The group's founder, Arron Banks, denies the claim and has said it will go to court to challenge the fine.
During a hearing of the Commons Digital, Media and Culture committee, the Commission's head of regulations Louise Edwards said investigations into Vote Leave, the lead Brexit campaign, and Better For the Country were "well advanced" and it expected to complete them this year.
The watchdog has rejected calls for a similar investigation into the lead pro-Remain group Britain Stronger In Europe, a decision which has angered Brexit supporters.
The regulator's director of political finance Bob Posner said it already had significant investigatory powers but would like them to be beefed up to bring it into line with other regulatory bodies.