An cross-party group of MPs pledged to investigate which banks refused to help the most financially vulnerable people in Britain.

The Treasury Select Committee said there needed to be greater transparency surrounding which banks were willing to open basic bank accounts for those who are financially excluded.

It came after the MPs were told many banks refused to let the poorest people open basic bank accounts vital for benefit payments and state pensions, while those who were able to open accounts were often hit with high charges.

About 2.8 million adults in Britain - one in 12 households - do not currently have a bank account.

About 68 per cent of those so-called financially excluded people live in 10 per cent of postcode areas. The Government hopes to halve the number of people without a bank account by the end of the year but, giving evidence yesterday, consumer groups said banks "actively discouraged" people from opening basic bank accounts.

Basic bank accounts enabled people to set up standing orders and direct debits but not overdrafts so people on low incomes or benefits do not risk falling into debt.

Mike Barry, debt project manager at the Citizens Advice Bureau, said: "Although at corporate level banks are committed to basic bank accounts, at ground level the individual banks are actively discouraging people from opening such accounts.

"One person who spoke to us was told these accounts were only open for the lowest of the low. There is a tendency for them to direct people away".