LONDON - ITV, Britain's biggest free-to-air commercial broadcaster, reported a 50% drop in adjusted earnings for the first half after the COVID-19 pandemic hit advertising revenues and interrupted the production of shows.

The company said ad revenue for the second quarter fell 43%, driving a 17% decline in total external revenue for the six months to the end of June to 1.22 billion pounds ($1.61 billion). Adjusted earnings before interest tax and amortization halved to 165 million pounds, it said.

Chief Executive Carolyn McCall said it had been "one of the most challenging times" in the history of the broadcaster.

"While our two main sources of revenue - production and advertising - were down significantly in the first half of the year and the outlook remains uncertain, today we are seeing an upward trajectory with productions restarting and advertisers returning," she said on Thursday.

ITV Studios paused the majority of its productions globally in mid-March as a result of COVID-19 restrictions, resulting in a 17% decline in total ITV Studios revenue to 630 million pounds.

It restarted production on its popular soaps "Coronation Street" and "Emmerdale" in June, it said, adding that of the 230 productions impacted or paused by the lockdown, around 70% have been delivered or were back in production.

($1 = 0.7590 pounds)

(Reporting by Paul Sandle; Editing by Sarah Young and Edmund Blair) ((paul.sandle@thomsonreuters.com; +44 20 7542 6843; Reuters Messaging: paul.sandle.thomsonreuters.com@reuters.net))