The UUP's defeated Westminster candidate in Fermanagh-South-Tyrone has said he intends to challenge the result, which he lost by 53 votes.
Mr James Cooper secured 17,686 votes to the 17,739 won by Ms Michelle Gildernew of Sinn Fein but claimed there was "clear and irrefutable evidence of electoral malpractice in some parts of the constituency".
The UUP claimed the polling station in the strongly nationalist town of Garrison, Co Fermanagh, was kept open for 30 minutes past the official closing time.
Mr Cooper said he was to meet his lawyers today to discuss options for any legal challenge. Any such challenge will go before a special election court headed by three High Court judges.
Although Mr Cooper would not discuss his legal options, they are believed to range from seeking to have late votes discounted to seeking a full by-election.
An inquiry into allegations of possible UUP misuse of postal ballots was also begun before the election after it was revealed some applications had been released to it before other parties.
Mr Jim Dixon, an anti-agreement unionist seriously injured in the 1987 IRA Enniskillen bombing, polled 6,843 votes, and Mr Cooper said there was "immense bitterness in the unionist community at the way in which he was used".