Mid-sized businesses are driving the UK's overseas revenue growth and have increased international turnover by 43 per cent over five years, new data has revealed.
The increase, from £105bn to £151bn, exceeds that of FTSE 350 companies that have seen a four per cent decline in overseas turnover from £418bn to £402bn over the same period.
London's mid-sized firms, which have a turnover between £10m to £300m, followed the trend and recorded growth of 66 per cent between 2013 and 2018,.
The capital's medium firms increased turnover from £29.3bn to £48.6bn, figures compiled by accountants and business advisors BDO showed.
Northern Ireland-based companies had the largest growth in overseas turnover at 135 per cent, followed by the South West England which recorded an increase of 73 per cent.
BDO managing partner Paul Eagland said: "High-performing and entrepreneurially spirited mid sized businesses are the economic engine of the UK.
"Despite much change and uncertainty over the past five years including the decision to leave the EU these businesses have continued to prosper internationally.
"As Brexit negotiations come to a close, it is crucial that government consider the needs of the mid-market to allow this growth to continue and to ensure businesses do not begin to lose their patience with policy-makers."
The UK's mid-market AIM-listed or private equity-backed businesses account for one third of all private sector revenue (£1.2tn) and 45 per cent of private sector employment.
Employee numbers at UK mid-sized firms have risen by almost a half, with London medium-sized businesses jobs increasing by 51.2 per cent.
Mid sized businesses in the West Midlands had the most significant lift in employee numbers where they increased by 63.5 per cent.
BDO has called for action to help boost growth after Brexit including investing in smart infrastructure and simplifying the UK tax system.
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