Engineering and technology recruitment specialist Gattaca's underlying pre-tax profits fell to £7.4m in the six months to the end of January - 21% down on last time.
Statutory net fee income fell to £35.4m - down 3% while underlying NFI was down 4% at constant currencies.
Statutory revenues of £304.2m were up from £297.9m.
Chief executive Brian Wilkinson said: "As previously announced, performance in the first half of the financial year reflects the tougher UK trading conditions post the EU Referendum in June 2016.
"The softening in NFI in the first half was driven by near term uncertainty which led to elongated hiring decisions and some projects being delayed; however, the medium-term outlook in our sectors remains positive with some signs of a return of confidence in recent weeks.
"The reduction in NFI has coincided with investments made in growing our international headcount and ensuring that the Group has the infrastructure to build a truly scalable business.
"Unanticipated one-time cost overruns and delays in realisation of back office cost savings have also impacted profitability in the period.
"Given the opportunities we see, the Group has continued to strategically invest in overseas sales headcount, up 26 since 31 July 2016 and we expect to see a return on these investments during the second half and beyond.
"In line with our vision to become the leading specialist Engineering and Technology recruiter, the acquisition of Resourcing Solutions Limited on 2 February 2017 has significantly strengthened our capability in the UK Rail market, an area of high investment by the government.
"With the integration of Networkers complete, we now intend to consolidate our central cost base, whilst maintaining the structure and support we have built and to convert the sales opportunities we see into growth over the short and medium term."
At 9:25am: (LON:GATC) Gattaca PLC share price was +1.88p at 273.88p