Britain’s main pro-EU campaign group has hired the digital strategists who ran the Conservatives’ general election social media campaign that reached 17 million people a week.

The In Campaign hopes that Tom Edmonds and Craig Elder, who were praised as the “secret weapon” of the Tories, will help it target middle-ground voters who will then swing the referendum.

The appointment of Edmonds and Elder was publicised as the organisation confirmed it would apply to the Electoral Commission to be designated the lead campaign group on the pro-EU side in the referendum.

The group hopes it will be in a strong position on grounds that it enjoys strong cross-party support. Will Straw, a Labour candidate in the general election, and Damian Green, the former Tory immigration minister, are playing lead roles in the campaign.

The In Campaign wants Edmonds and Elder to repeat their success in targeting key swing voters. For the last general election they produced online videos aimed at pensioners and aspiring home owners.

In a Daily Telegraph article after the election the pair contrasted their approach with Labour’s blanket strategy. They wrote: “It’s much better to reach five people with the right message than 500 with the wrong one. Labour talked a lot about having four million conversations in four months during the election campaign, which led to them focusing on quantity not quality. They got drawn into an irrelevant numbers game of their own making – and ended up just spraying and praying.”

In an echo of the Scottish independence referendum, held a year ago on Friday, the In Campaign believes the EU referendum will be decided by a cohort of 30-40% of the electorate who have yet to make up their mind on Europe. The rest of the electorate divide evenly between pro-EU and anti-EU voters.

Green said: “One of the Conservative party’s secret weapons in the 2015 election was Edmonds Elder: they know precisely the audience we need to reach and how we can mobilise thousands of activists to explain why Britain is stronger in Europe – and ultimately win the referendum.”

Straw said: “Tom and Craig are absolutely at the top of their game and bring a wealth of experience in digital campaigning and supporter engagement. This referendum on Britain’s place in Europe offers people one of the biggest choices in our history: whether to remain a part of the world’s biggest single market or to walk away, risking jobs and weakening our economy. Whilst no one claims Europe is perfect, the fact is we are stronger, better off and safer in Europe than we would be out of it.

“As the campaign gathers pace we will use the latest digital tools to communicate that choice to the public, and to make the case that we believe Britain is stronger in Europe.”

• This article was amended on 18 September 2015 because Will Straw and Damian Green work for the In Campaign, not Business for New Europe.

