Senator Ivor Callely and his family have built up an extensive portfolio totalling at least 19 properties, an Irish Independent investigation reveals.
The investments were mainly bankrolled by AIB, which provided finance for 15 residential properties owned or co-owned by Mr Callely, his wife and two of their children.
The Callelys invested heavily in the Dublin residential market over the past decade, land records reveal.
They could face the prospect of significant losses with property prices in some parts of the capital now half of what they were when the market reached its height in September 2006.
The revelation comes as a Seanad committee plans to mount an appeal against a High Court ruling that quashed Mr Callely's suspension for claiming more than €80,000 in expenses from his holiday home in west Cork.
Significantly, as many as 10 separate mortgage arrangements were entered into by Mr Callely and members of his family with AIB in 2006 and 2007.
Some of these arrangements were used to fund Mr Callely's involvement in a consortium developing beachfront apartments in Clontarf, Dublin -- a project that never got off the ground and subsequently went into receivership.
Six houses on Dublin's northside, including the family home in Clontarf, are registered in the name of the senator and his wife, hairdresser Jennifer Callely. All of those are subject to mortgages from AIB.
At least three of those properties are registered as rental properties with the Private Residential Tenancies Board (PRTB). One rental property in Artane is registered solely in Mr Callely's name, and has an AIB mortgage.
A further six Dublin homes are registered solely in the name of Mrs Callely, four bought using AIB loans and two bought with funding from Irish Nationwide. PRTB records show at least three of these homes are rental properties.
A residential property in Waterford city is also registered in Mrs Callely's name and is subject to an AIB mortgage.
The couple's holiday home in Kilcrohane, near Bantry, Co Cork, is also in Mrs Callely's name.
It was transferred into her sole ownership in April of last year. It is currently mortgage free and is on sale with an asking price of €650,000.
Mr and Mrs Callely and their son Ronan are registered as the owners of another rental property in Killester, north Dublin, bought in late 2006 and subject to an AIB mortgage.
The couple's daughter Aoibheann is also registered as the owner of two rental properties in Donaghmede, north Dublin, both of which were purchased with the aid of AIB loans.
Mr Callely made his sole foray into development land in 2007, joining a four-man consortium which acquired a Clontarf Road development property at a cost of €10m. Finance for the deal, which also involved Galway-based businessmen John O'Dolan, Denis Kenny and Daragh Sharkey, was provided by Investec.
The group planned to demolish the property and build 44 apartments, but the plan was rejected by An Bord Pleanala.
Investec subsequently appointed a receiver to the project. Mr Callely never publicly declared his involvement.
His Fianna Fail constituency colleagues, TD Sean Haughey and councillor Deirdre Heaney, both objected to the plan without knowing he was involved.
When contacted by the Irish Independent, the senator declined to comment on his political future or the property investments made by him and members of his family.
"I will make my decision in relation to my political future in due course pending consideration of all matters," he said.
"My family's business is private and should be so respected. Any matter that is required to be disclosed by me is disclosed in my annual return to the Standards in Public Office."