Taxpayers are underwriting hundreds of thousands of dollars in legal and consultants’ fees as a grand jury investigation into legislative bonuses unfolds.

Republicans and Democrats in the Senate and the House have hired outside law firms to represent them in the investigation by the state attorney general over whether bonuses were paid to staffers as compensation for campaign work.

The House Democrats have run up the largest bills so far — almost $500,000 in legal and consulting costs. It is unclear from House records what portion of that expenditure was strictly legal costs.

House Democrats have paid about $280,000 to Chadwick Associates, a risk management firm based in Washington that is headed by former state Inspector General Bill Chadwick, who has provided legal advice. He was hired in March and began providing legal advice in October.