The 'Ndrangheta mafia has formed links to senior Australian politicians, an investigation by Australia's Fairfax Media-ABC Four Corners found.

The Calabrian-based criminal organisation, which runs drug smuggling and extortion rackets worth billions, lobbied politicians through corrupt donors, according to the report.

A confidential police memo quoted in the report, claims the crime gang used well known party donors to put a "legitimate face" on its activities.

A man with "deep mafia associations" reportedly met then Prime Minister John Howard during a fundraising event for the Liberal Party in the early 2000s.

There is no suggestion that Howard was aware of the man's criminal links.

It alleges that mafia-linked party donors lobbied both Labor and Liberal politicians to secure advantages for the gang's legitimate and illegitimate businesses.

One lobbying campaign aimed to secure a visa for a mafia boss subsequently convicted for drugs trafficking and implicated in a murder plot, while the investigation also found the son of another alleged mafia boss secured a work experience placement at the Australian embassy in Rome.

The report outlines how loopholes in the Australian donations system leaves politicians exposed to corruption.

The 'Ndrangheta mafia is believed to be one of the world's wealthiest criminal organisations, with a drugs trafficking empire stretching throughout Europe and Australia and with links to Colombian cocaine cartels.