Ladbrokes has announced its pre-tax profits fell 66% in 2013 to £67.6 million, as it continues to overhaul its digital businesses.
As well as the slump, the company warned it will close between 40 and 50 shops this year.
The UK's second largest bookmaker blamed the hit on upgrades to its online gambling systems.
Developing gaming products used by smartphone or tablet users has taken longer than expected, the bookies said.
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The company posted a 63.5% plunge in bottom line pre-tax profits to £176.4 million on a comparable 52-week basis.