Tony Hayward, the former BP chief executive who runs Iraqi Kurdistan-focused Genel Energy, on Wednesday said oil prices are set to soar as Opec has taken just six months to stop the US shale oil boom in its tracks.

Speaking at the FT Commodities Global Summit in Lausanne, Switzerland, Mr Hayward said Opec had shown itself to be “the most successful cartel in history”, predicting oil prices would soon return to near $80 a barrel.

“The supply base is shrinking, they [Opec] are maintaining their market share. It seems like it’s been a big success,” said Mr Hayward, who left BP after the 2010 Deepwater Horizon oil spill.

Opec’s decision in November to hold production steady in the face of fast-growing US shale output helped accelerate the oil price collapse. But an increasing number of big oil executives and traders argued this week that the worst of the oil rout is over, having forced a quick response from the market.

The drop in oil prices from above $110 in June to near $45 in January has led to a marked reduction in the number of rigs drilling for oil in the US. Many energy majors and national oil companies have also slashed investments in production worldwide. On Wednesday, Ice June Brent was trading up 53 cents at $62.60 a barrel.

The heads of Vitol and Gunvor, two of the world’s largest independent oil traders, said on Tuesday that oil prices had probably bottomed.

“The low price is behind us,” Gunvor chief executive Torbjorn Tornqvist told a panel at the FT Summit.

Mr Hayward, who said he will take a less active role in the day-to-day running of Genel by the end of this year, said US oil output will soon slow or fall.

Between 2011 and 2014 US output grew by more than 1m b/d each year as prices above $100 a barrel allowed companies to develop the process of horizontal drilling and hydraulic fracturing — commonly known as fracking — to reverse a decades-long decline in US production.

Mr Hayward, who is also chairman of Glencore, the Swiss commodities trader, acknowledged some Opec members had been hurt by the price crash, but said longer term the cartel’s decision to maintain production had been justified.

“It’s having exactly the consequences they envisaged,” Mr Hayward said.

Saudi Arabia, Opec’s most powerful member, has denied it is directly targeting US shale output, but has said it is irrational for higher cost production to take an increasing share of the market.

Some traders are still urging caution, however, with US crude oil inventories sitting at an 80-year peak.