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 cheap over-the-counter painkiller taken by millions of people in Britain every day could have the hidden benefit of slowing down ageing.
Some four million Brits are expected to fly out of the UK over the festive period, along with many more using roads and railways.
Scientists believe they may have found the key to fighting HIV - and it rests in the immune system of llamas.