Section 20. The commission shall at all times keep full and accurate accounts of its receipts, expenditures, disbursements, assets and liabilities, which shall be open to inspection by any officer or duly appointed agent of the commonwealth or the municipality. The commission shall submit an annual report in writing concerning its operations to the legislative and executive bodies of the municipality within one hundred and twenty days following the close of its fiscal year. Such report for the fiscal year ending one year after acceptance of this chapter and for each fiscal year thereafter, shall include financial statements relating to the operations and properties of the commission maintained in accordance with generally accepted accounting principles to the extent applicable and audited by an independent certified public accountant or firm of certified public accountants.