Until last week, I knew exactly who I would be voting for. I live in Islington North, a safe Labour seat held by Jeremy Corbyn since 1983. I like him – his voting record aligns with most of my views – and I like Ed Miliband. (No, really. Even before anyone thought to Photoshop his face onto Robert Downey Jr’s.)

But on Friday, after a chance remark by a colleague, I completely changed my mind.

They’d mentioned Swapmyvote.com, a site launched last week which links up voters who agree to vote on each other's behalf. Generally, each pairing is made up of someone, like me, who fears their vote will be wasted in a safe seat, and someone in a marginal who wants to cast a vote for an unwinnable candidate, often from a small party. So far, over 1,000 people have signed up.

According to the Voter Power Index (which is calculated based on how likely a seat is to change hands) my vote is only worth one twelfth of a vote, compared to a national average of about a third. According to our election site May2015, my constituency is in the top 20 safest Labour seats in the country. So off I went to find someone who could make my vote count.

On arrival, the site asks you to choose a preferred party, and another you’d be willing to vote for. I entered Labour and the Greens respectively, plus my constituency, and the site threw up a range of options. I picked Bharat Malkani, a university lecturer in Bristol North West who wants to vote Green, but hopes Labour will boot out the sitting Tory MP.

A couple days later, Bharat messaged me on Facebook partly, I imagine, to be friendly, and partly because the site encourages you to make contact so you can make sure your swap partner is committed to the deal. I called him to discuss why he, too, was willing to vote against the grain come 7 May.

Bharat, like me, signed up for the site as soon as he heard about it, keen to escape what he calls a “rock and a hard place” in his constituency. He voted Liberal Democrat last time round (“I do feel guilty about that“), but as a lecturer was horrified by their move on tuition fees. Besides, the party's now dropped to third place locally.

That left him with Labour – a party whose recent statements on immigration (not to mention that mug) left him feeling “a bit sick”. Ideally, he’d be voting Green – he likes their policies, though isn’t convinced they can implement them. Generally, he views himself as “one of those people disillusioned with all parties”, yet not quite disillusioned enough to cast a protest vote for the Greens in his marginal constituency. Thanks to the site, I'll cast his vote in Islington North, and he'll vote Labour to give Bristol North West the best chance of a Labour win.

As you can imagine, the concept has its detractors. At best, it’s in a democratic grey area; at worst it’s a kind of backwards gerrymandering. The first entry on the site’s FAQs is “Is this legal?", to which the answer is broadly yes - informal vote swapping has been going on for centuries, apparently.

Then there’s the issue of voteshare: as a Labour supporter, should I be concerned that in this scenario, only one vote for Labour will be cast, whereas without the website two probably would have been? A lower voteshare could work against Labour in coalition negotiations, though as Bharat points out to me, votes on paper don’t mean much if you don’t have enough seats to govern effectively.

Overall, though, I feel the system is far more honest than traditional tactical voting, as everyone, however indirectly, is voting for the party they support. And, while it’s circumventing the system, it’s circumventing a system which doesn’t work once you throw smaller parties into the mix, or, depending on your point of view, at all.

As Joe Cox, founder of VoteSwap, a similar site aimed directly at swapping Labour and Green votes, wrote in the Independent:

There are tribal Labour and Green activists who will condemn us. Yet our success so far suggests that there are enough shared values for many voters to understand this is win-win for progressives. By swapping their vote, the Conservatives lose more seats, but tactical voters do not have to harm their favoured party. And until our system is fixed, what's not to like about that?

Bharat agrees that while he would have viewed voting Labour as tactical, he doesn’t put this in the same category: “I think it helps people vote the way they want to vote. It's nice that someone's acting on my conscience.”