Changes to the way the judiciary is run were hasty and not thought through, the head of the Bar Council has said.
New plans separate the judiciary from politicians like Lord Irvine
The comments from Matthias Kelly, who leads barristers in England and Wales, came after the government announced sweeping changes to the legal system.
These included the abolition of the post of Lord Chancellor after hundreds of years and the setting up of a new Supreme Court and an independent body to appoint judges.
The changes will come under a new Department for Constitutional Affairs (DCA), the organisation of which has been criticised by the Tories and even Labour MPs as "botched".
These are not changes that have been bounced on people
Labour Party Chairman
Although Mr Kelly said lawyers welcomed the principle of separating the law from politics, he was concerned the reforms were being implemented too quickly.
Mr Kelly said: "The scale of the changes takes your breath away and the speed is quite remarkable."
He said barristers were concerned about appointments to the new Judicial Appointments Commission, fearing it would end up full of "party hacks".
"It's about who's going to choose the people who choose the judges," he said.
Shadow deputy prime minister David Davis said the prime minister was treating the constitution as "his own personal bauble".
"The constitution, including the judiciary, is something that belongs to the country as a whole," he told BBC Radio 4's Today programme on Saturday.
"It is not something to be pushed around by a sort of Labour Party managerial by-product."
The Tories accused Tony Blair of treating the judiciary as "another pawn on his cabinet board".
There was also criticism of the changes from within the Labour Party.
Bob Marshall-Andrews, an MP and QC, said Lord Falconer - an unelected peer and close friend of the prime minister - should not have been
appointed as Lord Chancellor and head of the DCA.
Out: Michael Meacher, environment minister
In: Estelle Morris, arts minister
Promoted: Margaret Hodge, minister for children
Back: Chris Mullin
Out: Nick Brown
Mr Marshall Andrews said the changes appeared to be a "botch, which looks as though it has been put together in panic".
Tory MPs want a Commons statement to clarify the plans, first announced on Thursday.
But the constitutional changes were defended by Labour Party Chairman Ian McCartney, who said they represented a "fantastic move forward".
"The legal profession has demanded these changes. The Labour Party has consistently said over the last few years it wanted to make these changes - these are not changes that have been bounced on people," he told Today.
The reshuffle surprises continued on Friday, when former education secretary Estelle Morris returned to government as the new Minister for the Arts.
Margaret Hodge was appointed to a new post of Minister of State for Children and Michael Meacher resigned as Environment Minister after six years in the job.
Within hours of leaving government Mr Meacher said he intended to use his new-found freedom as a backbencher.
Ms Morris, who replaces Baroness Blackstone, quit the government last year, saying she felt she had not performed well in the role.
Following her return to government, she said of her new job: "I know I don't have a hugely strong background in this, so it will be a huge challenge."
Former minister Chris Mullin also rejoined the government as a foreign office minister.
Tories were angry after John Reid was appointed as health secretary, saying a Scottish MP should not be in charge of the health service for England.
Mr Blair has also faced criticism over his handling of the Iraq war, with an opinion poll for The Times newspaper suggesting a third of Britons are less inclined to trust him.
A large majority of those polled insisted the war was justified, however.