Nearly 27m people had restaurant or takeaway food delivered in the UK over the last six months, with a third increasing the frequency of their orders.
The concepts are most popular among young, urban-based adults with nearly two thirds of those aged under 35 placing orders at least once a week.
But CGA warned that restaurants risked customer backlash if they failed to adapt to the growing market.
More than a third of consumers think the standard of delivered food is worse than is served in restaurants, while four in five would be put off a brand by a bad delivery experience.
CGA said the report highlighted the need for venues to invest in specialist packaging and technology to keep food fresh.
“Delivery is becoming a threat to some restaurant operators – but a better way to look at it is as a massive opportunity,” said Jamie Campbell, CGA director.
“Those who can deliver high quality food speedily, with efficient service and at a good price point can drive incremental business.”
The report found that delivery of alcoholic drinks could be a major revenue driver for restaurants, with more than four in five people saying they would order a drink with their food delivery if the option was available.
In July Deliveroo announced a new partnership with drinks brands including Brewdog, Majestic Wines and Honest Grape to deliver alcohol within 20 minutes.
The ordering site – which operates in 84 cities across 12 countries – announced a £210m investment in its expansion last week.
It is also developing the Roobox concept, which will allow restaurants to offer delivery-only kitchens in certain areas.
“The industry’s big challenge now is to maintain consumer demand for eating out in restaurants while also meeting their needs when they choose to eat at home instead,” said Campbell.
“It is a fine and difficult balance, and the operators who can work out how to strike it will be best placed in years ahead.”