Three MPs are condemning the decision by Jersey's magistrates' court to send former senator Stuart Syvret to prison.
Liberal Democrat MP John Hemming tabled a Commons motion claiming Mr Syvret was the victim of "political persecution".
The 45-year-old has been jailed for 10 weeks after being convicted of contempt of court and breaking data protection laws.
Mr Hemming wants the British government to raise concerns about his treatment.
Mr Syvret was arrested after publishing a confidential police report into suspicious deaths at the island's General Hospital, containing the name and details of a suspect.
He argued there had been a "cover-up" and said he was acting "in the public interest".
John Hemming, along with fellow Liberal Democrat Bob Russell and former Conservative minister Peter Bottomley, said he has been jailed for "criticising the Jersey establishment for its failures to enforce the rule of law".
They say the sentence "is an attempt to frighten others away from raising concerns about the failings of the justice system in Jersey".
Mr Syvret stayed with Mr Hemming for six months while in self-imposed "exile" in the UK.
Mr Hemming told BBC Jersey he felt Mr Syvret wanted to make a point.
He said: "I'm not surprised because what he wants to do is see the rule of law properly instated.
"One of your problems in Jersey is you do not have judicial review on the Attorney General.
"Which means you cannot challenge the failings of the prosecutary apparatus to prosecute people who have committed real offences and not nonsense offences.
"He needs to highlight this and I understand all of that and I am not surprised that he wasn't going to compromise."