The National Audit Office (NAO) has called on Ofcom to improve its handling of the broadband switching process.
In a report into the communications regulator's performance, the NAO said it must do more to demonstrate value for money to the taxpayer.
The regulator must do more to understand why fewer customers in the UK change internet service provider (ISPs), it added.
"Improvements are needed" to the switching process, to ensure consumers fell confident enough to search for more attractive broadband deals, the NAO said.
"Ofcom should demonstrate sharper objectives and metrics to better link its costs with the outcomes it achieves," the NAO stated.
Earlier this year, Ofcom warned broadband providers of the need to advertise broadband speeds in good faith, following complaints of exaggerated download capabilities.
The regulator found that many ISPs were unable to deliver headline broadband speeds to the majority of their subscribers.