The report, From Lock Up to Start Up, written GLA Conservative group planning spokesman Steve O’Connell, identifies 3,275 empty garages owned between 10 housing associations across the capital.
These, the report says, could be converted into commercial spaces and rented out at competitive prices to small businesses such as cycle mechanics, carpenters and product designers.
The report calls on housing associations to work with the mayor to pilot the conversion of an initial 300 garages, with the idea to roll it out nationally should it prove successful.
The report says the cost of converting a garage into a business unit is about £26,000, which includes electrical rewiring, heating, insulation and internet connection.
If the unit was rented out at £60 a week, housing associations could make their initial investment back in approximately eight years.
The report acknowledges that not all sites would be suitable for conversion into business units.
Planning permission would need to be secured, so close dialogue between housing associations and boroughs would be vital to consider the impact on planning regulations, local planning priorities and the impact on the area such as parking spaces and traffic flow, it says.
"There will be some planning issues such as change of use and these would have to be addressed by individual boroughs," said O’Connell.
But he added: "Because of the benefits of this idea to small businesses and the London economy, I will be pressing to make sure that the provision for change of use to be looked at favourably in these cases is included within the London Plan."
But some housing associations said that creating homes not offices was their main concern.
In a statement, housing association L&Q said: "Our analysis has shown there are significant planning challenges to converting garages, the biggest being that most are not eligible to conversion for other uses. As a developer of houses, creating homes is our priority.
"We currently have a small pilot programme that is actively seeking to turn an identified group of disused garages into homes. We will assess this project in order to decide next steps."
From Lock Up to Start Up can be read here.