A new Ministry of Justice will go ahead next week as planned, even if ministers cannot get backing for it from senior judges, the lord chancellor has said.
Lord Falconer said judges had agreed 'in principle'
Lord Falconer told the Lords constitution committee it had been agreed the change was "in principle constitutionally acceptable".
Ministers want to introduce the new ministry without a parliamentary bill.
The Department for Constitutional Affairs will become the MoJ, and also run the prison and probation services.
The Home Office, which loses these responsibilities, will be left to concentrate on dealing with terrorism, security, immigration and policing.
Former lord chief justice Lord Woolf has warned that the lord chancellor - with his extra responsibilities as head of the MoJ - could find it harder to maintain the integrity of the court service and judiciary.
Judges and officials have been holding talks aimed at reaching an agreement with the government on safeguards.
Lord Falconer told the committee he was confident this would happen.
But Lord Justice Thomas, who has been negotiating on behalf of the judges, said "difficult issues of principle" had still not been resolved.
He added that it was "impossible to tell whether the working party will reach agreement on what should be done or whether the work will reveal, at least in the view of the judiciary, that the necessary changes cannot be made without legislation".
The government has ruled out using a parliamentary bill to introduce the reforms.
Senior judges, however, want their budget to be ring-fenced when the new department is created.
They fear they will come under pressure send fewer people to prison because of a shortage of prison spaces.
Lord Falconer said the judges knew "perfectly well" that the MoJ was going ahead on 9 May.
But this was "subject to certain safeguards being put in place"