Yes campaign groups National Collective, Radical Independence and Women for Independence are preparing for a burst of activity over the summer months, the Sunday Herald can reveal.

Increased activism will be timed to boost support for independence as the referendum campaign reaches its most critical phase.

Among events planned by National Collective is a four-day festival of "arts, culture and politics" at Summerhall in Edinburgh. It will include lectures by Robin McAlpine of the Jimmy Reid Foundation and Guardian journalist John Harris, a comedy showcase headlined by Hardeep Singh Kohli, and the launch of a new book with contributions from some of Scotland's leading authors and poets.

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The Radical Independence Campaign (RIC) will stage a series of lectures, including one by English constitutional reform campaigner Anthony Barnett, and intensify efforts to win over working-class swing voters in key constituencies.

Women for Independence plans a number of "co-ordinated national days of action", in which activists will discuss independence with undecided female friends and family members, and will publish a manifesto explaining why women should vote Yes.

With Better Together still ahead in the polls - and the referendum four months away - there is a growing sense of urgency among many independence campaigners.

National Collective director Ross Colquhoun said the Yes campaign had to show it extended beyond Yes Scotland and the SNP.

He said: "We hope our burst of activity this summer will help build cultural confidence in Scotland at a time when it is crucial the Yes movement demonstrates its momentum and broad-based popular support."

RIC organiser Jonathan Shafi said the key lay in persuading large numbers of low-income Scots to back independence. Shafi added: "This summer, RIC groups all over Scotland are going to step up their campaign of mass canvassing to reach tens of thousands of working-class Scots."

Kezia Kinder, national co-ordinator at Women for Independence, said the Yes campaign was still struggling with women voters: "Support for independence among women is still lagging, and polls show women make up the largest group of undecided voters," she said. "Over the next four months we must ensure that ordinary women's voices are heard."

The news that smaller Yes groups will take a bigger role comes less than a month after Stan Blackley, former deputy director of communities at Yes Scotland, said the official pro-independence campaign had been "left behind" by a "wider, bigger, better" grass-roots Yes coalition.

Blackley claimed the recent increase in support for independence had occurred "in spite of Yes Scotland, not because of it", saying: "Many of the best ambassadors for Scottish independence have no contact with Yes Scotland at all".

Blackley lost his job this year in a staff clear-out at Yes Scotland, fuelling reports it had become dysfunctional. Some senior nationalists are even said to have considered scrapping it altogether.

However, Toni Giugliano, Yes Scotland's sectoral groups co-ordinator, denied the organisation was being side-lined and praised the "creativity and enthusiasm" of smaller groups. He said: "Many have sprung up spontaneously, have grown organically and are self-sustaining. They are all inspiring in their own ways and along with the hundreds of local and community groups … they form the backbone of the whole campaign."