Theresa May will ask small businesses to set out what they want from Brexit negotiations so they can take advantage of the UK leaving the European Union.
The Prime Minister will host a roundtable with small and medium-sized enterprises with less than 250 employees and trade associations in Downing Street on Thursday.
She will ask for their views on how the Government can help them seize on any potential new opportunities offered by Brexit, particularly on exports.
Mrs May has created two new Cabinet posts with the appointment of Brexit Secretary David Davis and International Trade Secretary Liam Fox in an effort to develop and lead a strategy for leaving the EU.
She will also tell the firms they are the backbone of the country and central to the Government's aim to increase productivity, boost skills and create an economy open to new technologies.
Speaking ahead of the roundtable, the PM said: "From dynamic start-ups to established family firms, our small and medium-sized businesses are the backbone of our country.
"I want to build an economy that works for all, and that means working with, and listening to, smaller firms.
"The priorities I have set: a more productive, skilled workforce, an economy balanced across the UK and open to new opportunities, can only be achieved if we listen to these businesses.
"This isn't about dry economics.
"Britain's 5.4 million small and medium-sized businesses provide people with jobs, put food on families' tables and underpin the strength of our economy.
"They are a fundamental part of my vision of building a country that works for everyone, not just the privileged few.
"I also want those firms, across all the sectors of our economy, to be able to take advantage of the opportunities presented by Brexit, such as exporting to new destinations.
"So, I'll be asking them for their views on we get our whole economy firing ahead of Brexit."
The roundtable will be attended by the Federation of Small Businesses, British Chambers of Commerce, EEF, the Institute of Family Business, Small Business Saturday, Local Enterprise Partnership Network, the Association of Independent Professionals and the Self-Employed and individual small business representatives.
It comes after the first meeting of the new Cabinet committee on the economy and industrial strategy.
Mrs May spoke to workers at a south London business ahead of the summit.
She was joined by Housing and Planning Minister Gavin Barwell, whose brief also includes London, during a short visit to New Addington-based joinery manufacturer Martek.
Mike Cherry said the Federation of Small Businesses (FSB) will stress the importance for Brexit negotiations to focus on the needs of smaller firms.
The FSB national chairman said: "Our members want access to European markets, the ability to hire the right people, reassurance on key EU-funded schemes and a new approach to both regulation and de-regulation.
"We will also discuss how small businesses can boost their productivity in the emerging plans for the Government's new industrial strategy.
"Now more than ever, UK economic growth rests on the future success of our smaller businesses."