The youngest voter in the 2010 general election, 14-year-old Alfie McKenzie from Preesall in Lancashire, was entirely unremorseful today, despite a day of relentless teasing in school and a stern warning from his local police and council that his behaviour could constitute a criminal offence.

"It was just too much of a temptation to resist," he said. "I'm a socialist, I'm really, really interested in politics. I'd been reading up on it a lot before the election, and I'd got very interested in tactical voting. Nobody asked me for ID or anything, I was literally in and out of the polling station in about 15 seconds.

"As I said to my headteacher today, regrettably I'm only sorry that I got caught. I would be a Labour supporter, but I voted Lib Dem tactically: I would have been interested in a Lib-Lab coalition, but Clegg is in with Cameron right now, isn't he? I'm not really a Cameron man."

He was astonished when his polling card turned up in the post, a few months after his sister Georgie gave his name, along with hers and their parents, Nadine Wiseman and Darren McKenzie, to a woman who turned up at their front door with a clipboard. It was done in all innocence: Georgie thought it was about the census, but the woman was actually updating the electoral register for the Wyre and Preston North constituency.

Alfie's day began early on Thursday. "I was at the polling station by 10 past seven. I dressed really carefully, in my trenchcoat, with my glasses, and I was careful to wear my posh shoes. I put on a posh accent, sort of southern. I reckoned if they thought I was a Tory voter nobody would suspect me, because it couldn't have made any difference in this constituency."

He went home, changed into his uniform, and got the bus to St Aidan's school, where he made the fatal mistake of confiding in a few friends, and telling a teacher in strict confidence. "The teacher went straight to the head, and the head called the council – but I don't think the council had a clue what to do about it in the beginning."

A few hours later he was called out of English class to the head's office. It was when he spotted the police car parked in the yard that it dawned on him that he could possibly be in trouble. He was given a stern talking-to, but the police also rang his mother and confided the matter was unlikely to go any further.

Half an hour later he was called out of class again and told the Sun was on the phone and wanted to speak to him. "I'd never speak to the Sun," he said firmly, "I'm a Guardian reader."

He describes his household as "not political but people do have very strong opinions on what's right and wrong". His mother, a PA to a doctor, is a Labour supporter, and his father is a remarkable animal: a socialist estate agent.

Despite Alfie's best efforts, Ben Wallace held the seat for the Conservatives with a majority of 15,844. "Still, they were predicted to take the seat with 94% of the vote, and he only got 50%, so I like to think I helped a bit," said Alfie.

His mother, Nadine Wiseman, is finding it hard to take a suitably stern line on her son's behaviour. She said: "He's fabulous – there's never a dull moment with Alfie around."