Cultivation of opium poppies in Afghanistan has hit new records this year as Nato pulls out combat troops.

The United Nations Office on Drugs and Crime (UNODC) said opium production was up by 17% since last year.

Its Afghan Opium Survey 2014 said the area under poppy cultivation had risen by 7% to cover 224,000 hectares.

UNODC head Yury Fedotov warned there was a serious risk Afghanistan could become a narco-state, following the withdrawal of foreign forces.

Most poppies are still grown in southern Helmand province, where British troops were stationed until October.

The annual survey says the eradication of poppies has decreased by 63%.

Most of the opium poppies are grown in the south and west of Afghanistan, including its most insecure provinces, such as Helmand.

One of the reasons British troops were sent to Helmand was to help cut opium production.

Billions of dollars have been spent trying to eradicate opium poppies in Afghanistan since US-led troops ousted the Taliban in 2001.

In October the US government watchdog for Afghan reconstruction said the US had spent $7.6bn (£4.72bn) over 13 years trying to eradicate the plant.

Despite those efforts the report predicted further increases in cultivation.

The UN valued the Afghan opium crop at nearly $3bn (£1.86bn) in 2013, up 50% from 2012.

Cultivation has been rising yearly since 2010. Afghanistan currently produces more than 80% of the world's opium.