Opposition treasury spokesman Joe Hockey has defended MPs' entitlements, saying they are not overly generous.

A long-awaited review of parliamentary entitlements is expected to recommend a crackdown on MPs' study trips and other taxpayer-funded perks.

The review, handed to the government in April, forecasts entitlements will cost $373 million this financial years.

Mr Hockey defended the system, saying it covers the costs of the job.

"And when you represent more than 100,000 people as a member of parliament, the costs of doing business is expensive," he told Network Ten.

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"Ultimately you have got to pay for democracy."

AAP