Ofgem announced it will look at whether Iresa treated customers fairly in its call handling and complaints process.

The regulator will also look at whether customers in debt were given ample notice that money would be leaving their accounts, and whether Iresa checked if indebted users had the ability to pay money owed.

Further, Ofgem will examine whether Iresa enabled customers to switch suppliers and whether customer refunds were handled in a prompt and timely manner.

The move comes as concerns were raised with Ofgem relating to a high level of complaints against Iresa, including through Citizens Advice and Ofgem’s consumer affairs teams.

Charity Citizens Advice reported Iresa to Ofgem in November 2017 following complaints over billing, long phone queues and ‘inappropriately blocking customers from switching’.

Gillian Guy, chief executive of Citizens Advice, said: “According to our complaints handling data, Iresa is one of the poorest performing energy companies.

“New entrants to the market should face greater scrutiny. It’s currently too easy for new firms to set themselves up as energy suppliers, often before they are able to provide good quality customer service. Ultimately it is energy customers who pay the price when firms are not up to scratch.”

Ofgem will seek to clarify whether any rules were broken in relation to customer information and customer contact, though it added that the opening of this investigation doesn’t imply it has made any findings about non-compliance by Iresa.

YourMoney.com made several attempts to contact Iresa for a response but none was received.