The US venture capital industry, which has become an important source of capital for technology start-ups around the world, is facing a severe shake-out that will lead to a contraction in future investments, according to some of Silicon Valley’s leading financiers.

These warnings follow one of the weakest years ever seen for profit-taking by start-up investors, and come amid predictions of an even worse period ahead. Only six companies that were backed by venture capital went public last year, the lowest numbers since the 1970s.