Proposals to double the size of the economy in South Wales and the West of England have been announced. The Western Gateway – a cross-border partnership of 28 local authorities stretching from Swansea to Swindon – says its newly published ‘Plan for Sustainable Development’ could boost the UK by £250bn by 2050.

The plan, launched at a convention in Newport, includes improving rail connectivity, investment into nuclear energy and the creation of a hydrogen ‘supercluster’.

The paper also calls on the UK and Welsh governments to partner with the Western Gateway on the proposals, which are backed by numerous high-profile academics, business leaders and ministers.

Rebecca Evans, Welsh cabinet secretary for the economy, and Dame Nia Griffiths, parliamentary under-secretary of state for Wales, are among those who have pledged their support.

Sarah Williams-Gardener, chair of the Western Gateway, said: “This plan powerfully demonstrates that the Western Gateway is ready to help provide the solutions to support the Prime Minister’s national mission.

“Supported by business and our local authorities, this plan demonstrates the art of the possible and offers the UK and Welsh Government tangible opportunities to partner with our area to deliver growth for our communities.

“Our plan is promoting grass root solutions which can help unblock routes to new investment, support our innovative economy and better connect communities who are at risk of being left behind.”

The partnership recently published independent research which claims the Western Gateway could be the fastest-growing region outside of London over the next five years. It also found that, on average, businesses across the area miss out on between £3-9m of private sector investment every year when compared with other parts of the UK.

Cllr Huw Thomas, leader of Cardiff Council and vice-chair of the Western Gateway, added: “We know we have huge potential working together as the fastest growing economic area outside of London. Based on evidence, this plan demonstrates that we as a region are ready to be partners with governments in both England and Wales to provide the solutions to deliver for our economy.”

Next week (October 29), the Western Gateway will launch the ‘Plan for Sustainable Growth’ in Westminster in a bid to encourage the UK government to lend its support to the partnership.