The power company Norwich City Council is using to offer thousands of people cheaper renewable energy has been hit with a multi-million pound fine - after one of its traders manipulated UK gas prices.

City Hall has collaborated with French company ENGIE Power Ltd to create 'energy white label' company Roar Power.

People who switch to get their electricity from the service are promised gas and electricity from entirely renewable sources.

People can sign up to a community tariff, through which profits are reinvested into community support projects.

But energy watchdog Ofcom has just imposed a £2.1m fine on the French-based energy firm.

The regulator said a trader working on behalf of ENGIE increased prices to boost trading profits during a three-month period in 2016.

It said an investigation found ENGIE was involved in a form of market manipulation called "spoofing", which involves placing bids or offers to trade with no intention of executing them, to increase or decrease prices.

Ofgem said it took place from June to August 2016, and involved a number of bids and offers to trade concerning a natural gas contract on the UK wholesale gas market - which broke market manipulation rules.

Despite the breach of energy market integrity and transparency legislation, the investigation found no evidence of more widespread market manipulation by ENGIE.

Ofgem said the energy provider "failed to take appropriate measures" to prevent the breach from happening or detect it.

While the regulator said ENGIE did have some measures in place, it added they were inadequate.

Ofgem said the company co-operated with investigations and has taken measures to prevent this type of price manipulation happening again.

ENGIE said it "strongly condemns practices that distort the market" and had new measures to detect such practices and prevent them being repeated.

A city council spokesman said "We were unaware of the investigation; we work alongside a different section of ENGIE and have no dealings with the wider organisation.

"We remain committed to our mutual goal of providing renewable, competitively-priced energy to the people of Norwich and beyond."