DUP MP Ian Paisley has dismissed as "utterly pathetic" a claim in a new BBC documentary that his father financed a UVF bombing.
In a lengthy broadside, he branded it a "filthy story" against the late former DUP leader Ian Paisley with "absolutely no credible evidence".
The North Antrim MP said his mother, Baroness Eileen Paisley, is "incandescent" over the forthcoming broadcast.
He said the "most hurtful" aspect was its planned airing just days before the fifth anniversary of his father's death.
In the BBC Spotlight programme to be aired on Tuesday, a retired British army commander claims the late Mr Paisley financed a UVF bomb in 1969 at a reservoir in Killkeel, Co Down.
Former British army company commander David Hancock was stationed close to Silent Valley when the bomb exploded, cutting off part of the water supply to Belfast.
He told the programme that an RUC inspector based at Killkeel showed him evidence that the bomb was financed by the former firebrand preacher turned Stormont first minister.
Read More: BBC documentary lays bare brutal political and military history of the Troubles
Responding to the claim, Ian Paisley Jnr described it as "complete and total poppycock" and said the "link is so tenuous that it's see-through".
The MP said his father was in jail for civil disobedience in 1969 and would not have been able to finance such an attack.
He said the claim is "third-hand gossip from an unnamed police source and unrevealed police material of gossip that a solider says he picked up on from a policeman".
"The story is untrue. There is absolutely no credible evidence or basis upon which to make these allegations," he told BBC Radio Ulster's Nolan Show.
Mr Paisley added: "He had no access to finance. He wasn't a financier of terrorism. He wouldn't have been able to get his hands on the sort of resources that are being described here. It's just utterly pathetic."
The North Antrim MP said he has spoken to his mother about the claims, who has "completely dismissed them out of hand" and is "incandescent that the BBC would do it".
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He said "the thing that is probably most hurtful and disgusting and filthy about this particular story" is its planned airing days before the anniversary of his father's death.
"That's particularly hurtful to my mother and particularly hurtful to the rest of our family," he added.
He also said his family was not contacted by the BBC to be given an opportunity to respond to the allegations.
A BBC spokeswoman said: “The BBC has complete confidence in the editorial integrity of the programme. As no allegations were made against the wider Paisley family it was not necessary to offer them a right to reply.
“The series leads our autumn programming and was scheduled to follow on from BBC Northern Ireland’s portfolio of news-related content recognising the 50th Anniversary of troops entering Northern Ireland in 1969.”
The Spotlight documentary, to be aired on Tuesday on BBC One, is the first in a special series of programmes on the Troubles.
It also contains previously unseen footage of a young Martin McGuinness, a former IRA commander, carrying weapons and standing beside a car as a huge bomb was loaded into the back.
The bomb was driven into Derry city centre and exploded, causing damage to property.
