A court in Milan began proceedings yesterday to decide whether David Mills should stand trial over claims he accepted a £350,000 bribe from ex-Italian PM Silvio Berlusconi.
The estranged husband of Culture Secretary Tessa Jowell said he had new evidence that would "demolish" an Italian corruption case against him.
Prosecutors claim the money was a payment for giving "favourable evidence" for the politician at two of his previous corruption trials.
Mr Mills - an international lawyer - will not attend the hearing but insisted a raft of new paperwork proved beyond doubt the cash was not linked to Mr Berlusconi.
"We have been able to get together all the relevant documents. We now have a complete audit trail back to 1992 which shows exactly who this money came from, what happened to it," he said.
"It excludes totally the possibility that it came from Mr Berlusconi or anyone connected to him. The evidence completely demolishes the prosecution case."
Mr Mills - who split with Ms Jowell after she was drawn into the controversy over his financial affairs - hit out at the prosecution.
It had been an "overtly political act", he said, timed to coincide with the Italian general election - in which Mr Berlusconi's party was narrowly beaten by rival Romano Prodi.
"I just hope it's also quick and decisive," he added, suggesting the hearings could take up to several weeks to conclude.
Mr Mills has insisted that the £350,000 came from a Neapolitan shipbuilder called Diego Attanasio.