The UK risks falling behind in key technologies such as AI and semiconductors if the government doesn’t urgently overhaul its policies and regulations, a group of almost 1,000 technology companies has warned.

TechUK, a lobby group whose membership includes Alphabet Inc., Amazon.com Inc. and Apple Inc., said in a report published Tuesday that Britain was a “broken” economy for growing startups and described its regulation as “expensive and awkward.”

The report underscores growing doubts over the UK’s post-Brexit attractiveness to business, at a time when homegrown companies like Arm Ltd. are looking abroad for investment and growth …