Metro Bank promises to revolutionise the banking experience by offering retail opening hours, unparalleled service and a simple range of products suitable for everyone.

The bank will be closed on only four days of the year - Christmas Day, New Year's Day, Good Friday and Easter Sunday - and will open from 8am to 8pm Monday to Friday, 8am to 6pm on Saturday and 11am to 4pm on Sunday.

It promises customers it will take just 15 minutes to open an account in one of its branches, including obtaining a credit or debit card, which will be printed in store.

The group, which opened its first branch in Holborn, London, was co-founded by US billionaire Vernon Hill and Anthony Thomson, chairman of the Financial Services Forum, and is based on the model used for Commerce Bank in the US which was founded by Mr Hill in 1973.

Metro Bank plans to open a second branch in Earls Court next month, with 10 further branches opening in Greater London during the next two years, expanding its network to more than 200 outlets within the M25 during the next decade.

The branches will have toilets, free coin-counting machines and, in what is thought to be a nod to its dog-owning financial backer Mr Hill, will allow dogs and provide them with a bowl of water and a bone.

Craig Donaldson, chief executive of Metro Bank, told Sky News: "We're going to win customers by wowing them.

"Over 40 per cent of customers are dissatisfied with their bank at the moment and over a third said they would switch their bank if there was a viable alternative.

"We are that credible alternative - we're open seven days a week, 361 days a year, we're open early and late and you can come in and get your cheque book and debit card in 15 minutes. That's how we're going to get people to switch."

But critics were unimpressed with the bank's products, which include an instant-access savings account offering a return of just 0.5%, compared with a best-buy rate of 2.8%, as well as a three-year fixed rate bond paying only 3%, significantly below the market leading rate of 4.3%.

The group's mortgage offering is equally uncompetitive, with a two-year variable rate mortgage for someone with a 40% deposit of 3.5%, while a two-year fixed rate deal for the same borrower is 4%, compared with best-buy rates of 2.29% and 2.99% respectively.

It also raises mortgage rates by 1% for people looking to borrow up to 80% of their home's value, while current account charges interest of 15% on overdrafts, compared with an industry average of 14.1%.

However, its personal loan rate of 10% is more competitive, although still not a best buy, while it is charging interest of 13% on credit card purchases and cash advances, compared with an industry average of 18.5% for purchases and 25.6% for cash.

David Black, of financial information group Defaqto, said: "It's going to be a slow burn to get moving in terms of market share. Its products aren't going to trouble the best-buy tables."

He added that as the group was not using risk-based pricing, under which rates for unsecured credit vary according to a customer's credit rating, they were likely to have to turn down a lot of applicants.

Michelle Slade, of Moneyfacts.co.uk, said: "Although they are offering all these other benefits, such as longer opening hours, one of the main things for people is a competitive interest rate.

"If they haven't got at least a reasonable rate of interest people will discount them. They are going to struggle to get market share."