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.
At the time, Mr Paterson insisted he was “totally innocent” of breaking lobbying rules and that the process did not “comply with natural justice”.
In response, Labour MP Chris Bryant, who chairs the standards committee, insisted Mr Paterson had been given “every opportunity” to put his case across – and his arguments had been heard “respectfully and fairly”.
In her report, the Kathryn Stone described Mr Paterson’s actions as “an egregious case of paid advocacy” and recommended he be suspended from the House of Commons for 30 days.
Conservative MPs initially sought to block the suspension with the backing of No 10, but Downing Street reversed its decisions after an angry backlash.
Mr Paterson subsequently announced his resignation from Parliament saying he wanted a life “outside the cruel world of politics”.
The row severely damaged then-Prime Minister Boris Johnson’s reputation, and is one of the factors that led to his eventual downfall.
In 2014, Mr Paterson argued in a speech that the UK should not just quit the EU but also replace the European Convention on Human Rights, on which the European Court of Human Rights adjudicates.
Downing Street said the government would “respond in the normal way” but that it was not able to comment on legal proceedings at this stage.