Andrea Coscelli, the chief executive of the UK's Competition and Markets Authority, tells the BBC that tech giants Google and Facebook have too great a share of the UK online advertising market and that regulation is needed. In this extended interview with Amol Rajan, Dr Coscelli also gives his response to Facebook's recent behaviour in Australia after a new law was proposed which would force tech companies to pay publishers for news.

In response to this interview, Facebook said it faces "significant competition" online from rival firms and that "it’s always been our intention to support journalism in Australia and around the world, and we’ll continue to invest in news globally and resist efforts by media conglomerates to advance regulatory frameworks that do not take account of the true value exchange between publishers and platforms like Facebook".

Google has also been approached for comment by the BBC.

Producer for BBC News: Elizabeth Needham-Bennett