Orobator's lawyers say her trial in Laos was "a disgrace"
Lawyers representing a pregnant British woman convicted of drug smuggling in Laos have demanded her release, calling her trial there "a sham".
Samantha Orobator, 20, from London, was given a life sentence and transferred to a UK prison earlier this month under an agreement between Britain and Laos.
The human rights group Reprieve is to challenge her conviction.
Ministers say sentences imposed abroad must be served to ensure other overseas UK prisoners are allowed to return.
Orobator, from Peckham, was spared the death penalty in Laos because she is pregnant.
She claims to have artificially inseminated herself while in prison. Her baby is due next month.
Reprieve has branded her trial "disgraceful". It said Orobator was forced to sign statements and was not given an independent lawyer in Laos.
The lawyers say their client was convicted after a very brief trial that did not hear her defence.
Clare Algar, from Reprieve, said: "As a vulnerable young woman far from home, Samantha was exploited by a government determined to convict her.
"The Lao government's handling of this case revealed their contempt for truth, decency and legal rights.
"We hope the British government recognises that Samantha's life must not be thrown away simply to placate that regime."
Her solicitor, Rhona Friedman, said Orobator had been denied a fair trial: "Samantha was subjected to a sham legal process that makes a mockery of justice.
"The Lao conviction is manifestly unsafe and should not be recognised in this country."
A preliminary hearing of Orobator's case will take place at the High Court next week.
A spokesman for the Ministry of Justice said it did not comment on individual cases.
But he added: "The United Kingdom is normally required to continue to enforce the sentence imposed by the sentencing court.
"Prisoner Transfer Agreements enable prisoners to serve sentences, imposed abroad, in their own country.
"Under these agreements the receiving state undertakes to continue to enforce the sentence imposed by the sentencing state.
"Without these agreements British nationals would be required to continue serving their sentence in prisons abroad."
Orobator's pregnancy meant she avoided Laos's mandatory death penalty for drug smuggling, although no-one is thought to have been executed in the country since 1989.
She named the father of her baby as a British man from Bradford, John Watson. The 47-year-old is still in prison in Laos after his conviction for drug smuggling.
The Foreign Office, which says it has concerns about Watson's health, is in talks with Laos about his transfer to the UK.