The re-election of a Tory councillor by a majority of one has sparked controversy after a ballot paper marked with the word “Brexit” was counted as a vote for the Conservatives.

Stephen Hirst retained his seat in Tetbury Town in the Cotswolds, defeating independent Kevin Painter by 232 votes to 231.

The voter is said to have written “Brexit” with a large arrow pointing towards Hirst’s name – ruled to be a vote for the Tories despite a backlash against Theresa May for delaying the UK’s exit from the EU until October.

Painter is considering challenging the result in court, saying it was “Blackadder-esque”, “bizarre” and had “brought the integrity of the local election system into question”.

Hirst, a former mayor of Tetbury who reportedly once assisted the Metropolitan Police investigation into phone hacking after the Sun newspaper published a story about him allegedly swapping wives with his neighbour, has been contacted for comment.

The returning officer Nigel Adams insisted he was following Electoral Commission guidance, which states a ballot paper should not be deemed void “if an intention that the vote shall be for one or other of the candidates clearly appears”.

He said: “Prior to the final adjudication on the doubtful papers, the number of votes for the Conservative candidate and the independent candidate were level. 

“However, when adjudicating on those ‘doubtful’ papers, the returning officer awarded one additional vote to the Conservative candidate, having regard to the guidance contained in the Electoral Commission’s booklet on doubtful papers and examples within election law books.” 

But Painter said: “Surely after a few counts where the vote is tied, how democratic is it then allowing a paper that had previously been rejected to be admitted? Especially when there was no cross in the box for voting. Are not the rules quite simple?” 

Painter continued: “Since when was a spoilt ballot paper used to decide a result other than by being rejected. […] I am not often speechless but this is unbelievable.”

Painter is now considering whether to launch an election petition to the Royal Courts of Justice.

He has 21 days to submit his application but will have to pay up to £2,500 in “security for costs”.

Ultimately the process could lead to a trial.

Despite Hirst’s victory, the Liberal Democrats took control of Cotswold District Council from the Conservatives.