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Researchers have identified the London Tube routes where passengers are most likely to catch the so-called "commuter cold."

The widely accepted concept that cramped, busy tubes and stations are a hotbed for spreading flu-like symptoms has never been officially scientifically proven.

But, a new study undertaken by the University of Bristol has now shown Tube travel is linked to the spread of infectious diseases.

By comparing Oyster card route information and Public Health England data on flu-like illnesses, Dr Lara Goscé and Dr Anders Johansson discovered higher rates of airborne infections in Londoners that have longer Tube journeys through busier terminals.

"There has never been a proper dialogue on this," Dr Goscé said.

Transport for London said that Tube is an "extremely safe" environment and that trains and stations were professionally cleaned throughout the day and night.

The findings highlighted the difference in infection rates for commuters from boroughs better or worse served by Tube lines.

For instance, infection rates in residents of Islington, who often change lines at crowded King's Cross St. Pancras, were nearly three times higher than in commuters from Kensington, who mostly take direct trains.

"If a borough is less served by underground lines than others, then commuters usually have to switch lines in very crowded junctions such as London Bridge or Victoria Station," Dr ;Goscé said.

"But those who live in boroughs such Kensington or Chelsea, their trip is very fast and very short so they don’t get in contact with as many number of people."

Because the data is just a sample, Dr Goscé said she was as yet unable to identify which boroughs were at the highest risk of being exposed to infectious diseases based on which lines serviced them.

The researchers hope the study will help spark further research and help inform government epidemic policies.

"It would be ideal to have a bigger sample of data so we could have a proper description of the city," Dr Goscé said.

"The other thing would be to implement this study with other biology studies to see exactly how the bug spreads."

She added: "policy makers, in particular, should address the role potentially played by public transport and crowded events and avoid encouraging the attendance of such environments during epidemics."

Transport for London said policies are already in place to lessen the spread of bacteria.

Jill Collis, Director of Health, Safety and Environment for TfL, said: “The Tube is an extremely safe environment and our trains and stations are professionally cleaned throughout the day and night.

“There is no cause for customers to worry about viruses and bacteria on the Tube or do anything different in terms of hygiene than they would in other public places.”

The research contradicts survey findings from 2013 by the London School of Hygiene and Topical Medicine, which found that catching public transport does not increase the risk of getting the flu.

But, Dr Goscé said the studies were conducted differently.

"We did a mathematical analysis and we had a model and analysed data while the other study was self-reported and, on a larger scale, the point where people get infected can get lost," she said.