A senior US politician has written to the head of the Securities and Exchange Commission raising concerns about how incoming European trading rules will affect US firms’ access to capital markets.

Congressman Dennis Ross wrote to Mary Jo White, chair of the SEC, on June 24. In the letter, seen by Financial News, he outlined concerns that proposed EU rules over the payment of research could "disrupt research coverage for US small and emerging growth companies, as well as their access to the capital markets".