Sir Scott Baker told the Commons home affairs select committee that while he had spent a week meeting US officials he did not meet the families or supporters of those facing extradition to the US.
Gary McKinnon, a computer hacker who has Asperger’s syndrome, has fought a six-year battle against extradition to the US on charges that he hacked into US military computers in 2002.
Babar Ahmad has been held in Long Lartin prison for seven years without charge or trial fighting extradition to the US on alleged terror charges.
Campaigners have called for the two to be tried in Britain as that is where the alleged offences are claimed to have occurred.
Mr Baker told the committee that he had not found time to meet those campaigning on behalf of Mr McKinnon and Mr Ahmad before completing his report.
Committee chairman Keith Vaz asked why that was the case when “you managed to go to Washington for a week.”
The former judge said he had received written submissions from all those with an interest in the treaty.
Parliament voted this month for an “urgent reconsideration” of the law, under which Britain allows extradition to the US on the grounds of “reasonable suspicion” while the US will only allow extradition to Britain if there is “probable cause.”
Questioned by the committee on this issue Mr Baker said “you couldn’t put a sheet of tissue paper” between the tests in each country.
It emerged last month that evidence collected by the Metropolitan Police in the Babar Ahmad case had been given to US prosecutors instead of being handed to the Crown Prosecution Service to investigate whether he had a case to answer.
Green Party MP Caroline Lucas said the Crown Prosecution Service must obtain all of the files from the US authorities and review them completely.
She also called for a public inquiry.