Jeremy Corbyn is expected to outline how Britain can deliver prosperity outside the EU when he hosts an alternative Brexit summit tomorrow.

The Labour leader is due to set out his vision of a post-Brexit Britain when he delivers a major speech in London.

He will be speaking just hours after the declaration of results in two crucial by-elections in Stoke Central and Copeland. Voters in both seats chose to leave the EU in last year’s referendum although the campaigns to replace Tristram Hunt and Jamie Reed in the Commons have not been dominated by Brexit in the way initially anticipated when they opened in January.

Corbyn will attempt to move on from Labour’s embarrassing rows over article 50 – which prompted the resignation of Clive Lewis, Jo Stevens, Rachael Maskell and Dawn Butler from the shadow cabinet – by delivering the speech at an event for those who have been marginalised by the debate in Britain.

Earlier this month Labour’s leader imposed a three-line whip in the run-up to the Commons vote on the Brexit bill but ultimately 52 Labour MPs voted against moving the formal trigger to leave the EU.

The proposal for tomorrow’s event came out of Corbyn’s meeting with representatives from the Party of European Socialists (PES), Labour’s sister organisations, in October.

Now Corbyn is expected to set out more of Labour’s economic approach to life outside the EU when he addresses a gathering of business and trade union leaders, NGO staff and socialist MPs from Britain and the continent.

Earlier this week John McDonnell, the shadow chancellor, used a keynote speech to call for a “manufacturing renaissance” to boost Britain’s economy in the aftermath of Brexit. He highlighted Germany’s Mittelstand, which has helped to deliver prosperity through backing for medium-sized businesses.