The parliamentary aide to Northern Ireland's Secretary of State is expected to be sacked after voting in favour of a referendum on Europe last night.
Despite the support of 483 MPs, David Cameron suffered a major assault on his authority as he was hit by a significant revolt by furious Tories. The rebel bid to pressure the Government into staging an in/out EU referendum may have been overwhelmingly rejected, but 111 MPs still voted for the motion - including all eight DUP members.
But the Commons defeat will provide minimal comfort for the Prime Minister, who failed to convince many disgruntled Tories that he backed their aims, but the timing was wrong.
Before defying his own Government, Stewart Jackson - the parliamentary private secretary to Northern Ireland Secretary Owen Paterson - admitted it would mean he loses the "baubles of ministerial office".
"When is the right time?" he asked. "If not now, when?"
The DUP's Nigel Dodds criticised party leaders for ordering MPs to vote against a referendum.
He said: "It's deeply disappointing that on an issue like this, that the whips have been so vociferous from all the parties.
"While the vote may be won today by the party leaders, the people can't be denied their democratic vote."
Independent MP Lady Sylvia Hermon backed the call for a referendum, while the SDLP's three MPs all opposed the motion, as did Alliance's Naomi Long. Foyle MP Mark Durkan criticised the focus on the UK's future in the EU, while the Eurozone was facing a crisis.