Former TD Seymour Crawford has claimed Sinn Féin has attempted to defame both himself and Fine Gael, by claiming a man who challenged Mary Lou McDonald on her party's pensions policy in Dublin on Friday was his brother.

The man was identified as being Fergus Crawford, CEO of the Irish branch of asset management firm Sarasin & Partners.

Former Cavan-Monaghan TD Seymour Crawford said both his brothers pre-deceased him, and that Fergus Crawford was not related to him at all.

"I was extremely surprised and annoyed, because I think this is an effort to defame my character and that of Fine Gael by the Sinn Féin party.

"I had only two brothers, both deceased (John in 1998 and the Reverend Joe in 2014), and have no relation called Fergus Crawford - good, bad or indifferent."

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An unsuspecting Mary Lou McDonald engages in a not so brief encounter with a member of the public on Grafton Sthttps://t.co/XBplNKFvvN

— RTÉ News (@rtenews) February 19, 2016

Sinn Féin deputy leader Mary Lou McDonald accused "concerned citizen" Fergus Crawford of having "some brass neck" after his position emerged.

She said: "The bankers, developers, all of the crew who wrecked this place have now regrouped, and they are now sufficiently emboldened to challenge people like me on the streets of Dublin on the basis of, ironically, our ability to protect ordinary people.

"There's a big irony in that and I know it isn't lost on anyone. The man is of course entitled to his view."