The rush to pass new laws means ministers do not put enough effort into getting their plans right in the first place, says a committee of peers.
Critics say the red tape laws have constitutional dangers
The Lords Constitution Committee accuses the government of "lamentable" attempts to consult on new laws aimed at cutting red tape.
It says ministers failed to recognise the constitutional impact of the plans.
The peers welcomed changes to the Legislative and Regulatory Reform Bill but said more safeguards are needed.
The bill is aimed at allowing ministers to change laws to scrap burdensome regulation quickly.
But critics of the initial proposals said it gave ministers free rein to change historic laws, including even Magna Carta, without full Commons scrunity.
Despite the government's concessions, the rail regulator this week attacked the plans, saying it could undermine the independence of regulators and deter investors by creating uncertainty.
Water regulator Ofwat says it shares those fears, raised by chairman of the Office of Rail Regulation Chris Bolt.
The Lords Constitution Committee says the way the bill has been handled is an "indictment of the processes of policy-making and legislative".
Its report says getting law plans right should have priority over passing them quickly.
"We acknowledge that the government has adopted an open approach to listening to critics and has brought forward several new clauses, but this is no substitute for well-planned legislation," it says.
The peers criticise ministers for trying to rely on assurances that the bill would not be used to scrap laws in controversial cases.
Such pledges are not binding on future governments, they say.
Committee chairman Lord Holme of Cheltenham said: "While simplifying and repeal of regulations is a fine aspiration, the government got it badly wrong this time.
"They wanted to give themselves the power to change any law with the minimum of parliamentary involvement, thus gold-plating their powers.
"They should have known that was constitutionally questionable."
Lord Holme said constitutional change should only be made through the full law-making process in Parliament, not by ministers using delegated powers.
"The simple fact that ministers failed to recognise the profound constitutional importance of the Legislative and Regulatory Reform Bill does not inspire confidence that they would not use delegated powers to introduce constitutional change in the future, without even realising what they are doing."
The peers say they are still not sure the bill strikes the right balance between helping worthwhile legislation be passed and ensuring effective scrutiny in Parliament.
The House of Lords starts debating the plans next week.
A Cabinet Office spokesman said the government would carefully consider the recommendations in the peers' report.
"The bill as passed by the Commons on 16 May put it beyond doubt that the powers will only be used for the better regulation agenda that is so important business, public services and voluntary organisations," he said.