Ontario Provincial Police say they have charged former Vaughan mayor Michael Di Biase with breach of trust and municipal corruption after an investigation that's lasted four-and-a-half years.

Di Biase, 71, of Woodbridge in Vaughan, is due to appear in a Newmarket courtroom on Oct. 30.

The investigation by the OPP's economic crime and corruption squad began in April 2015, following a referral to police by the city's integrity commissioner and a complaint by local Vaughan activist and Di Biase political rival Richard Lorello.

Lorello had raised concerns that it appeared Di Biase was getting help building his family cottage from a construction firm called Maystar General Contractors — a company that has received more than $150 million in business from the City of Vaughan since 2002.

Last year, the OPP commander overseeing the investigation told CBC News that officers were focused on "the circumstances surrounding the construction and expert consultation, and the payment for those services," on Di Biase's cottage.

Court filings obtained by CBC News show investigators had been looking into any "advantage or benefit" Di Biase might have received from Maystar General but also another construction company and an architecture firm.

Maystar General Contractors has consistently denied it had any hand whatsoever in the building of the cottage, and the OPP has previously said that the companies it was interested in were "simply being viewed as witnesses" and were never subjects of the investigation.

The cottage is located on Orr Lake, about 25 kilometres north of Barrie.

The OPP said it won't comment further on the charges.