Police have launched a formal investigation into two Victorian MPs who claimed about $130,000 in expenses to live by the sea instead of in their electorates.

Speaker Telmo Languiller and Deputy Speaker Don Nardella both resigned on February after it was revealed they claimed a second residence allowance to live far away from the Melbourne CBD and their electorates.

Shadow attorney general John Pesutto wrote to Chief Commissioner Graham Ashton in March, asking for an investigation.

Police on Wednesday confirmed they are are moving forward with a formal investigation.

"Both matters that were referred to Victoria Police in March have been assessed and have now progressed to the investigation stage," a Victoria Police spokeswoman said

"As the investigations are ongoing, we will not be commenting further."

The second residence allowance is designed to support country MPs who live more than 80km from the city and who maintain a second home in Melbourne.

Both Mr Nardella's and Mr Languiller's electorates are within 80km of the city.

An audit by accounting firm Pricewaterhouse Coopers in March found gaping holes in the rules that allowed the two Labor MPs to claim the perks.

The audit found Mr Nardella had been claiming the allowance since 2010, first for living in country Ballarat and later in seaside Ocean Grove after a relationship breakdown.

Mr Nardella initially quit the Labor Party rather than agree to Premier Daniel Andrews' demand to pay back the $98,000 relating to the Ocean Grove claims.

But the member for Melton, who remains on the crossbenches, has since agreed to a payment plan that includes regular deductions and a $16,000 lump sum.

President of the Legislative Council Bruce Atkinson said police had sought information from the parliament about the work of the audit committee.

Mr Languiller, the member for Tarneit in western Melbourne, claimed the allowance when he moved to Queenscliff in 2016, also after a breakdown in his relationship.

He repaid the $38,000 in full in March shortly after the scandal broke.