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.
More top news
A possible ninth planet at the edge of the solar system could be the reason behind one of the biggest mysteries in astronomy.
Philip Thomas was a 10-year-old pupil at Pantglas Junior School in Aberfan when a coal tip collapsed and slid downhill.
The chief executive's resignation comes amid controversy about allegations of doping in cycling.