Dr Sanjib Bhakta, one of the study's authors, from Birkbeck's department of biological sciences, said: "Despite a concerted global effort to prevent the spread of tuberculosis, approximately 10 million new cases and two million deaths were reported in 2016.

"In searching for new anti-bacterials, we tend to focus on molecules that are potent enough to be developed commercially as new drug entities by themselves.

"However, in this study we show that by inhibiting the key intrinsic resistance properties of the TB, one could increase the effects of existing antibiotic treatment and reverse the tide of already existing drug resistance."

Prof Simon Gibbons, another of the authors, and head of UCL's department of pharmaceutical and biological chemistry, said: "Natural products from plants and microbes have enormous potential as a source of new antibiotics.

"Nature is an amazingly creative chemist and it is likely that plants such as the Persian shallot produce these chemicals as a defence against microbes in their environment."

In October, England's chief medical officer, Prof Dame Sally Davies, urged global leaders to tackle the growing threat of antibiotic resistance.

Medical experts say these drugs are being used too much, and that 25,000 people die across Europe each year because of drug-resistant infections.

Researchers said they hope the molecules, which were tested in a laboratory, could be combined with existing antibiotics to form new anti-TB drugs.

The research is published in the journal Scientific Reports.