Jeremy Corbyn has met children at a lunch club in Swansea to highlight Labour’s policies for young people, in the latest of a series of campaign-style stops as his party gears up for a possible snap general election.

The Labour leader claimed the government was “failing a whole generation of children” and vowed his party would “unlock the potential of every child, not just a lucky few” as he helped to serve lunches, alongside the MP for Swansea East, Carolyn Harris.

He pointed to Labour policies including extending free school meals to all primary schoolchildren, ending the benefits cap, and building 1m affordable homes.

Boris Johnson’s government has already made a string of manifesto-ready promises, on everything from boosting police numbers to improving hospital food, fuelling speculation that he is preparing for an early poll, either after Brexit day – or earlier, if he is forced into it.

Corbyn meanwhile hopes to tempt back many of those remain supporters who deserted the party for the Liberal Democrats and the Green party at May’s European elections.

Labour agreed a more forthright Brexit position before the summer, which has seen Corbyn repeatedly promise a referendum – and allowed key shadow cabinet figures including Diane Abbott and John McDonnell to say publicly they would campaign for remain.

Corbyn is poised to table a motion of no confidence in Johnson’s government when MPs return from their summer break in early September.

If Johnson lost the vote, there would then be a two-week period for a government that could command a majority to emerge.

Corbyn has proposed to other MPs wanting to stop no deal that he would lead a time-limited “caretaker” administration to request an extension to article 50, which would then dissolve itself and call a general election.

He plans to discuss the idea at a meeting with other anti-no-deal MPs on Tuesday, though some, including the former Conservative Nick Boles, have declined the offer.

Labour’s chances of success are also in doubt, with some potential Tory rebels tempted to stay their hand, given Johnson’s insistence in Berlin and Paris this week that he is seeking a deal.

The Green MP, Caroline Lucas, wrote to Corbyn on Friday to accept his invitation, however, and urged others to follow suit.

Lucas said she would support the idea of Corbyn as a temporary PM but also urged him to make way for an alternative candidate if he cannot command a majority. It follows the Lib Dem leader, Jo Swinson’s insistence that she could not support a Corbyn-led government, even temporarily.

“I am prepared to support Jeremy Corbyn as leader of this caretaker government, as should any MP who wants to stop a no-deal Brexit. But if he cannot gain the support of a sufficient number of colleagues across parliament, I hope he will be prepared to back another MP from his party, or another, who can. I will ask him again to make his position clear in our discussions next week,” she said in a letter to Corbyn.

She also said she would continue to make the case that a fresh Brexit referendum should be held before any general election.