Ali Dizaei has become the most senior police officer to be convicted of corruption offences.

Former police Commander Ali Dizaei has been sentenced to four years in prison after being found guilty of “misconduct in public office and perverting the course of justice”.

The Independent Police Complaints Commission (IPCC) launched an investigation into Iranian-born Dizaei after a member of the public submitted an allegation of misconduct against the officer to the Metropolitan Police Authority (MPA).

Yesterday the Crown Prosecution Service (CPS) convicted Dizaei of falsely arresting a web designer – 24 year old Waad al Baghdadi – in a dispute over money and then lying in official statements when he claimed he had been assaulted and threatened by the man.

According to the IPCC when Mr al-Baghdadi tried to get the £600 Dizaei owed him for some work he’d done on his website, the police commander assaulted then arrested him and lied about the entire event.

“If he [Dizaei] had been successful, Mr Baghdadi may have been sent to prison,” said Nick Hardwick, Chair of the IPCC.

“Dizaei behaved like a bully and the only way to deal with bullies is to stand up to them. Mr Al Baghdadi has shown tremendous strength of character throughout this case. We are grateful for the confidence he placed in the IPCC and, as a result of that, justice has been done today.”

Commenting on the verdict, Metropolitan Police Service (MPS) Commissioner, Sir Paul Stephenson, said: “It is extremely disappointing and concerning that this very senior officer has been found guilty of abusing his position and power.

“The public expect the police to treat them fairly and honestly and we are resolved to tackle corruption at every opportunity. He has breached that trust and damaged not only his own reputation but that of the entire police service.”

However, 47 year old Dizaei continued to maintain his innocence and after the verdict he told the Guardian it was “completely outrageous and a fit up”.

The Metropolitan Police Authority (MPA) has refused to comment on the verdict.

This is not Dizaei’s first allegation of corruption. In 1999, just months after joining the Met Police as a Superintendent, Scotland Yard’s anti-corruption squad launched a covert investigation, resulting in Dizaei being suspended from duty in 2001. After being acquitted by an Old Bailey jury in 2003, he was reinstated by the Met in a deal that apparently followed government pressure.