A parliamentary committee on Thursday accused British Prime Minister Theresa May's government of giving ministers "excessively wide" powers in new bill to transfer EU law into British law.

The bill in question sets out the government's plan for transposing European Union law into the British statute book as part of Brexit.

But it creates scope for ministers to alter legislation without full parliamentary scrutiny in order to make sure laws works properly once transferred.

"The bill gives ministers excessively wide legislative powers beyond what is necessary to ensure UK law works properly when the UK leaves the EU," said a statement accompanying a report by a committee of lawmakers from parliament's unelected upper chamber, the House of Lords.

The government has said the powers created by the bill are strictly limited to what is needed to allow for a smooth transition - something they say is necessary to give businesses certainty over the rules they will face when Britain's EU membership ends in March 2019.

Nevertheless, May, whose Conservative Party does not have an outright majority in parliament, could be forced into making concessions to ease concerns from across the political spectrum to clear the remaining lawmaking stages.

Thursday's critical report by the House of Lords Delegated Powers Committee set out an alternative proposal that would allow more rigorous scrutiny of changes that the government wants to make when transposing EU law.

The report offers a taste of the resistance May can expect to find in the House of Lords, where her Conservatives peers are significantly outnumbered by rivals from other parties.

The Lords will have to approve the withdrawal bill before it can become law.

Earlier this month the government cleared the first of many parliamentary hurdles, winning a vote on crucial legislation known as the EU withdrawal bill despite criticism that it amounted to a government power grab.