(Bloomberg) - The U.K. will begin publishing a table Wednesday ranking utilities by the average cost of energy bills in a bid to spur greater competition for consumers.

The ranking is designed to encourage energy users to swap suppliers by showing them where they can benefit from cheaper prices, the Department for Energy, Business and Industrial Strategy said in an e-mailed statement. The Competition and Markets Authority said last year that British consumers overpaid on their bills by $1.5 billion a year from 2009 to 2013 by not changing suppliers.

“Millions of people across Britain continue to pay too much for their energy,” Business Secretary Greg Clark said in the statement. “The measures announced today are a positive step to help more people benefit from increased choice and competition. As the government has made clear, where markets are not working for consumers -- in energy or otherwise -- we are prepared to act.”

Ministers have been trying for years to break the stranglehold on the U.K. energy market of the so-called Big Six utilities, which provide power and gas to about 86 percent of customers, according to data from the energy regulator, Ofgem. The share of the six companies -- SSE Plc, Electricite de France, Iberdrola, Centrica, RWE and EON - is down from 99 percent in 2012. Last month, Chancellor of the Exchequer Philip Hammond hinted at more measures to come when he delivered his mini-budget, known as the Autumn Statement.

“We will look carefully over the coming months at the functioning of key markets, including the retail energy market, to make sure they are functioning fairly for all consumers,” Hammond said.

Ofgem will publish the first table online at 10 a.m. on Wednesday, enabling consumers to compare their energy bill with deals available at the 10 cheapest suppliers, it said.