On-the-door breathalyser schemes already run in 12 boroughs across London, and 76 venues across the capital have been voluntarily trialling breathalyser tests - and there has been a reported drop in violence since their introduction earlier this year.
The mayor has been asked if schemes would be rolled out in London in a style similar to the system introduced in Croydon last year.
Costs and benefits
Speaking at Mayor's Question Time on 16 December, he said: "I certainly don't want to be breathalysed every time I walk into a pub. Let me see whether we think it can deliver. We will have to consider the costs and benefits.
"I think it might be something that late-night entertainment business will welcome but some of them might think it is a bit of a burden, so let's see."
The opinion on breathalysers in the industry has been split, with some suggesting such tests would be damaging for pubs but others arguing they are a useful tool for door staff.
Breathalysers aim to stop binge drinking and give venues a tool to turn away customers. The usual limit is two or three times over the drink-drive limit.
The Metropolitan Police supports the schemes. Earlier this year, Sergeant Ian Martin, a licensing officer, told the Publican’s Morning Advertiser (PMA) that with violent crime rates on the rise, pubs and late-night venues need to work with police to make customers' nights out safer.
"Much of the time, violence is driven by alcohol. We're living in an age of diminishing resources and budget cuts. We need to find new ways to help premises," he said.
But the British Beer and Pub Association has warned breathalysers could turn pubs into "fortresses", encouraging drinkers to stay at home, while the Association of Licensed Multiple Retailers fears they will criminalise customers and lead to "unintended negative consequences".
The Apple & Parrot in Torquay, Devon, has been breathalysing customers since last year.
Apple & Parrot general manager Matthew Jarrett said the on-the-door tests have been a "fantastic" tool for the venue.
Jarrett said the tests no longer bother customers and are used by door staff to "double check" whether someone attempting to enter the pub is drunk.
Figures supplied by Devon and Cornwall Police said that, in December 2014 — when the breathalyers were first introduced in 23 venues — violent crime fell by 22%, violent crimes against the person (excluding domestic abuse) was down 39% and there were 10 fewer admissions to hospital compared with December 2013.
In London, breathalysers have been introduced in Westminster, Kingston, Wandsworth, Lambeth, Croydon, Havering, Enfield, Islington, Kensington & Chelsea, Hackney, Newham and Harrow.
Outside the capital, they have also been introduced in Norwich, Truro, Nottinghamshire and Leicestershire.