Liberal Democrat deputy leader Daisy Cooper has used her party’s conference in Brighton to present a 30-page plan intended to remove barriers to business growth. Cooper, who is also the party’s Treasury spokesperson, said the UK was being held back by a “computer says no” approach that made it harder for ideas, start-ups and research to develop domestically.

She said too many businesses and projects that began in Britain ultimately moved overseas. Cooper argued that the country had strong potential but that its systems were preventing investment, innovation and the development of skills. Her proposals are aimed at making it easier for companies, particularly small and medium-sized businesses, to start and expand.

A central measure would be a digital one-stop shop for businesses and investors. Cooper said the service would bring together tax, regulatory, legal, Companies House and other general business services. She proposed placing it within a new Department for Growth, which she said would simplify red tape and help smaller firms compete.

Cooper also proposed a Growth and Defence Partnership with the European Union. She described closer European ties as the “single biggest growth lever” available to the UK and said the partnership would cover economic and defence cooperation. In her speech, she called for agreements on the single market, a customs union and defence.

Cooper claimed that Brexit was currently costing the UK £90bn a year in lost tax revenue, and said a new relationship with the EU could begin to reverse that economic damage. The figure and the wider assessment were presented by Cooper as part of her argument for closer European integration.

The Liberal Democrat deputy leader positioned her party between Labour, the Conservatives and Reform UK. She criticised what she described as Labour tax rises and opposition parties’ spending cuts, while attacking Chancellor John Healey’s recent speech as lacking vision and ideas. She also criticised the Conservatives and Reform, including their economic record and support for the Liz Truss mini-budget, and warned against Nigel Farage becoming prime minister.