Ex-minister Owen Paterson is taking the UK government to the European Court of Human Rights over a standards watchdog verdict that he broke lobbying rules.
He resigned from Parliament last year after he was found to have abused his role as an MP while working for two firms as a paid consultant.
The ex-Tory MP is taking legal action in Strasbourg over the investigation, which he says was unfair.
The UK government says it is aware of the court action.
Mr Paterson, a leading Eurosceptic who once campaigned for the UK to break away from the European Court of Human Rights (ECHR), argues that the standards watchdog ruling "damaged his good reputation".
In a European court listing, he argues the investigation, by Parliamentary Commissioner for Standards Kathryn Stone, was unfair because it did not hear from witnesses and met in secret.
The former MP for North Shropshire also says he was only given 15 minutes to address the commissioner, was not permitted to be represented by a lawyer and had no right to appeal.