Deputy Prime Minister Nick Clegg has ordered an immediate probe in to allegations that banks are discriminating against pregnant women by refusing them loans or mortgages.

Equalities Minister Lynne Featherstone is charged with investigating banking policies towards women and reporting back with an action plan to fix any problems.

The banks are also accused of charging women in business higher interest rates on finance.

The claims come from a paper for think-tank the Institute for Public Policy Research by Professor Noreena Hertz, which looked at the attitudes of bankers towards women and how this affected lending policies.

She accuses banks of discriminating against pregnant women and those on maternity leave, who are asked whether they are returning to work and about future family plans when seeking to finance a home.

In many cases, the banks insisted women returned to work before they could sanction a loan.

Hertz also reveals women entrepreneurs can expect to pay 1% higher interest on business borrowings than men. Men also have a slightly better chance (5%) of having a loan agreed and less rigorous lending terms.

Noreena Hertz said: “While certain aspects of banks’ behaviour have been interrogated in the wake of the financial crisis, how banks treated and continue to treat women customers is a subject that has received little attention.

“I’ve uncovered evidence which shows that women face discrimination from banks when they are seeking business loans or applying for mortgages. It’s as if we’ve gone back in time to the 1950s. Banks need to be put on notice that such behaviour is both unlawful and unacceptable.

“It is also economically damaging to the UK as a whole.

“The Prime Minister has stressed that if the economy is to grow then entrepreneurs need to be able to access credit. It is imperative that women be able to play their full part in the economic recovery.

“I am calling for an investigation into banks’ treatment of female entrepreneurs, pregnant women and women on maternity leave, and for banks to publish their lending decisions by gender in a transparent fashion.”