The UN estimates that a third more cocaine was being produced in the country in 2016.
The head of the UN Office on Drugs and Crime, Bo Mathiasen, called the increase significant.
Analysts say much of it was due to the end of the eradication of coca crops by spraying.
The report said the total coca-growing area rose from 96,000 hectares in 2015 to 146,000 in 2016.
Mr Mathiasen said that he held out hope for a reduction in cultivation because Colombia had signed a peace agreement with the biggest rebel group in the country, the Farc, which controlled much of the drug-producing areas.
But local analysts argue that the rise was caused partly by a hiatus resulting from the government's  peace deal with Farc rebels.
Under the deal, the Farc agreed to relinquish control over drug production areas and help the government try to encourage local farmers to plant substitute crops.
Farmers have taken advantage of the delays while the crop substitution policy is set up to plant coca, which has increased in price by almost 50%, because they know they will be offered subsidies later not to grow the plant.
Meanwhile, the Colombian government has increased by almost 50% its seizures of cocaine - from 253 tonnes confiscated in 2015 to 378 tonnes in 2016.

Joseph Pilates dedicated his life to refining the system of physical exercises he created whilst detained at the Knockaloe camp near Peel.
Organisers said Pilates' methodology had "benefited millions worldwide".
Pilates spent about three and a half years interned at the camp, which was designed to hold about 23,000 people.
The Knockaloe camp was divided into 23 compounds, each designed to hold 1,020 internees.
Organisers recreated that figure for the one-off 45-minute class.
A spokeswoman said the class had been inspired by seeing a postcard depicting internees putting on a Pilates display, just 15 days after he arrival at the Knockloe camp.
During his time in the camp it is believed the young Pilates worked in the camp's hospitals and was highly respected.
He spent his time developing a comprehensive system of physical exercise which he called "Contrology".
Mo Sherring, of the Isle of Man Pilates Studio, said it is "not just a series of exercises" but a "conceptual approach to movement".
Pilates invented his own unique apparatus formed from the springs from his dormitory bed.
He also studied the movement of animals.
After the war he dedicated his life to refining his methods which are still used widely across the world.

The 33-year-old former Stevenage and Fleetwood player made 52 league starts for Cambridge over the past two years.
He has signed a one-year contract with Mark Cooper's side.
"I was involved in two successful promotion campaigns [with Stevenage and Fleetwood]. I'd love to have a third," Roberts told BBC Radio Gloucestershire.
Speaking of the former Crewe youngster, who has also played for Accrington, Rovers boss Cooper added: "He is a good, solid defender and he'll give our younger players that little bit of guidance."
Cambridge chief executive Jez George told their club website: "Since arriving at the club, Mark has been an absolute professional, on and off the pitch."
On Wednesday, Forest Green confirmed the departure of midfielder Rob Sinclair by mutual consent.
Find all the latest football transfers on our dedicated page.
The United Nations says there was a 50% increase last year in the area of land being used to cultivate coca leaf in Colombia.
[NEXT_CONCEPT]
More than 1,000 people have taken part in a Pilates class at the place where its German creator was interned on the Isle of Man in World War One.
[NEXT_CONCEPT]
Forest Green Rovers have signed defender Mark Roberts after his contract at Cambridge United was cancelled by mutual consent.