Metro Bank said its residential mortgage borrowers will be able to rent their properties through Airbnb and similar websites for up to 90 days a year, without needing to seek permission from the bank first.
The offer applies to both new and existing customers, who can take the 90 days as they see fit, either split up into sections or as one block.
There is no particular loan-to-value that mortgage customers need to have in order to qualify and existing customers do not need to do anything to get the offer as it will be automatically applied, Metro Bank said.
Commenting on the move, David Hollingworth, a spokesman for mortgage broker London and Country, said it shows lenders are adapting to changes in society and the growth of the "sharing economy".
Mr Hollingworth said it could help to differentiate Metro Bank from its competitors in the mortgage market, where rates are already generally very low, adding: "Perhaps we will see more lenders starting to adapt to this situation."
Mr Hollingworth said that in general, mortgage customers wanting to regularly let out their property should check the small print in their mortgage contract to make sure they are complying with the terms and conditions of their home loan.
Metro Bank said that while it has no requirements about whether the mortgage customer needs to be present in the property when it is being let out, customers are advised to check with their freeholder that they have the right to let, as well as have appropriate insurance in place, before letting out their property.
Paul Riseborough, chief commercial officer at Metro Bank, said he hoped the announcement "will give our customers the reassurance they need to jump in and take advantage of everything the dynamic sharing economy has to offer".
Another recent innovation from Metro Bank means that customers and staff who do not identify with a specific gender can now use the title of Mx when filling out forms, rather than just having options like Mr, Mrs and Miss.
The bank highlighted its "strong" results for the third quarter of this year, which saw lending up 73% year-on-year to £5.2 billion and deposits increase to £7.3 billion, up 66% compared with September 30 2015.
James McClure, general manger at UK and Ireland Airbnb, said: "The way people use their homes is changing and this is an exciting step change from one of the UK's most innovative banks.
"We hope this triggers further support from the mortgage industry as we work together to provide real economic benefits for people and neighbourhoods."