Contrastingly, FTSE 350 firms saw a 7% drop in profits to £100bn.
Mid-sized businesses also enjoyed an 11% rise in overseas turnover to £135bn, compared to the 2% decrease for large businesses to £371bn and 11% drop for small businesses to £11bn.
BDO partner and chair of the Brexit taskforce Stuart Lisle called mid-sized businesses the “unsung middle” of the economy.
“Too big to benefit from incentives aimed at SMEs and too small to grab attention like FTSE companies, entrepreneurial mid-sized businesses fall into a policy and profile black hole,” he said.
Lisle urged the government to do more for the businesses, saying, “Measures such as creating a simplified tax system, investment in the right infrastructure projects and improving access to skills” would benefit them and also assist other sectors in becoming more successful.
In September, HM Revenue and Customs launched the Growth Support Service, which would provide tax support for 170,000 mid-sized businesses.