The government’s plans for reforming whiplash claims today attracted criticism from parliamentary scrutineers who fear too much power is being delegated to justice ministers and officials. The House of Lords delegated powers and regulatory reform committee said the lord chancellor should not be solely responsible for defining whiplash and setting damages for those who suffer it.

A tariff system for compensation – likely to result in significantly reduced amounts – is a key feature of the Civil Liability Bill, due for second reading in the Lords on Tuesday.

The government does not have to accept the committee’s recommendations, but the report makes it more likely amendments will be made before the committee stage starts on 10 May.

The cross-party committee, chaired by Conservative peer Lord Blencathra, said that by any standards the bill is ‘skeletal’ and agreed the use of delegated powers will ‘severely limit parliamentary scrutiny’ as the full details cannot be debated.

Members said whiplash had to be more accurately defined after extensive consultation and that definition must remain accurate.

Their report added: ‘It does not follow that the definition of ‘whiplash injury’ should be contained in regulations rather than the bill.

‘Neither the lord chancellor nor the Ministry of Justice is best placed to make this determination, which depends on medical expertise and clinical judgment.’

The committee had similar reservations about letting the lord chancellor set the tariff for injury damages, adding this was an ‘inappropriate’ delegation of power.

The report said: ‘We are not convinced that the lord chancellor will make a better job of this than the judges, who have had decades of experience dealing with damages for personal injury at the bar and on the bench.’

Simon Stanfield, chair of the Motor Accident Solicitors Society, said he was pleased that peers had echoed long-held concerns about elements of the reforms being delegated to ministers and officials.

He added: ‘Such major and detrimental changes to the way in which accident victims seek the justice which they deserve must be fully transparent and the detail debated openly.’