Andrew Gwynne campaigning in his Denton and Reddish constituency.Labour has created a sophisticated new social media tool that will allow it to target individual voters with tailored policy messages, the party’s campaigns chief has told the Guardian.

With the party more than 20 points behind in the opinion polls, Labour hopes using new campaigning methods, together with its army of almost half a million members, will help it to get a hearing with the public and disrupt the narrative that the Tories are on course for a thumping victory on 8 June.

Andrew Gwynne, who is Labour’s joint national elections coordinator, said: “One of the things that we’ve learned, particularly from Sadiq Khan’s campaign in London for the mayoralty, is that we can now use social media in a very sophisticated way, targeting the people that we want to reach out to with certain messages, certain policy announcements.”

The new tool called Promote is linked with Labour’s voter database. “We can identify specific people in a constituency that candidates will be able to target a message to,” said Gwynne.

He gave the example of so-called Waspi women – those born in the 1950s, whose state pension age has been changed. “We can now, using Promote, identity the Waspi woman in a particular constituency and we can let them know what Labour’s policies are.”

The Conservatives heavily used targeted advertising on social media during the 2015 general election campaign, and the leave campaigns in last year’s EU referendum attributed their success partly to their use of online messaging.

Gwynne said: “This is probably the first election where social media will probably have a significant impact”. He said Labour believed Facebook to be a much more effective platform for campaigning than Twitter, which could be “a bit of an echo-chamber”.

Gwynne insisted he was bullish about Labour’s prospects as he spoke in his constituency of Denton and Reddish in Greater Manchester on Friday, where he was launching his campaign for re-election alongside neighbouring MP Jonathan Reynolds.

He said Labour’s mass membership, which dwarfs the other major parties, would be a huge asset over the next seven weeks, dismissing the gripes of some Labour MPs that new party members do not come out and knock on doors.

Gwynne said: “We mustn’t forget that the Labour party as a membership has grown massively in recent years. They joined for a purpose: they joined because they believed in a new kind of politics, a new way of doing things – changing politics for the better. There is a general election. This is the chance to ensure that that Labour message of fairness, of a society for the many, not the few, is put out there. We will use every mechanism there is to get that message out there.”

Labour is scrambling to get candidates in place for many seats, including the dozen where the sitting MP will not stand for re-election. But Gwynne said applications would close on Sunday and all candidates would be in place by the end of next week, with the final decisions made by a panel of Labour’s national executive committee.

“The situation is that the NEC have now decided a timetable for fast-tracking selections because we can’t go through the normal process because of the closeness of the poll,” Gwynne said. “We will have candidates in place for the whole of Great Britain by the end of next week.”

Jeremy Corbyn campaigns in Cardiff.
Jeremy Corbyn campaigns in Cardiff. Photograph: Mark Hawkins/Barcroft Images

He said shadow cabinet ministers would be spread across the country campaigning on “flying-start Saturday”. Despite fears that Labour could be on course for its worst general election performance since 1935, Gwynne insisted the party was not simply fighting a defensi

Jeremy Corbyn spent Friday campaigning in the key swing seat of Cardiff North, where he said voters should draw inspiration from the party’s Welsh history. The Labour leader praised the community spirit of mining communities and said: “The principles of the National Health Service were born in the valleys of Wales. We are a party of hope and opportunity for everybody.”

Corbyn set his goals for flying-start Saturday , saying: “We’re asking Labour party members to get out on the streets and we’re hoping to get a million leaflets delivered in one day. The message is fairly simple: we’ve had enough of this Tory government, enough of the inequality and injustice that goes with it and we offer something very different.”