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 cloudy and damp start for many southeastern areas, but turning brighter through the afternoon.
Countries have been switching off their lights for Earth Hour, a global call for international unity on the importance of climate change.
Captain Steve Smith admitted Australia deliberately tampered with the ball during the third Test against South Africa.