Following the first count of votes for the seat, UKIP were believed to have defeated Labour by fewer than 10 votes. However, following a second count, Coun Wallis emerged as the clear winner, with a majority of almost 500.
Multiple sources close to the count told the Local Democracy Reporting Service (LDRS) that some Yorkshire Party votes were put together with ballot papers indicating support for UKIP.
One described the mishap as "careless", adding they'd "never seen anything like it" at an election count.
Speaking one week after the polls, Coun Wallis, who has been on Wakefield Council since 2000, confirmed that the error had occurred but insisted he had no hard feelings about it.
He said: “Unfortunately some of the votes got crossed, and UKIP appeared to have got a few more votes than me.
“There’d just been a mix-up with some of the ballot papers.
"We queried it and and then it was sorted, as it turned out after the recount that I’d won.
“I think it was just one of those things. I’m not angry about it all.
"It was just one of those mistakes that can happen. At least we got the right result in the end!"
Coun Wallis thanked his constituents for re-electing him and said he would continue to stand up for them on local issues, including improving Castleford town centre and protecting bus services.
Asked what he thought after he was informed he may have lost his seat, he said: "I’ve seen councillors before, who no matter how hard they worked, have lost their seats because of politics.
"I thought that had happened to me and that’s what was going through my mind."
On the night, UKIP failed to get any of their seven candidates elected in Wakefield, having lost their last remaining councillor last year.
The Yorkshire Party came within 100 votes of unseating Labour in Pontefract North, but similarly failed to make a breakthrough into the council chamber.
Local Democracy Reporting Service