The Office of Fair Trading (OFT) must improve its enforcement of competition law, a committee of MPs has urged.
The OFT last week called for a fresh probe into the supermarket sector
Members of the cross-party Commons Public Accounts Committee (PAC) have also called on the OFT to complete its investigations more quickly.
The PAC said the OFT still had "internal shortcomings" which are "limiting its overall effectiveness".
The OFT last week called for a new probe into the supermarket sector. Its annual budget today totals £56m.
This is a 70% increase since 2000.
The PAC said the OFT is still not maximising value for money, adding that it has been too reliant on complaints as the basis for investigations, and should instead use its own initiative more.
"Competition helps consumers get a good deal," said the PAC's chairman, Conservative MP Edward Leigh.
"The Office of Fair Trading, the main body for enforcing competition law and preventing anti-competitive behaviour, is at a critical point as it responds to being given increased powers and substantially greater resources.
"It produces good work and has a strong reputation. But it needs to rouse itself if it is to demonstrate that the extra resources are good value for money."