Serious flaws have been identified in a key part of what is understood to be Chris Froome's defence against a potential doping ban.

Last month it emerged that the legal team representing the Team Sky rider had submitted a new scientific study that claims the test for asthma medication is itself 'fundamentally flawed'.

Froome has been battling to save his reputation ever since he failed a drugs test for excessive levels of Salbutamol en route to his victory in last year's Vuelta a Espana. The four-times Tour de France winner who stormed to victory in last month's Giro d'Italia to secure his sixth Grand Tour title was found to have double the permitted limit of 1000ng/mL in his system.

Chris Froome (right) has been preparing for a tilt at a fifth Tour de France title this week

But the findings of researchers at the Centre for Human Drug Research in Leiden in the Netherlands was heralded last month as a major breakthrough in Froome's bid to clear his name.

Published in the British Journal of Clinical Pharmacology, the research paper claimed as many as 15.4 per cent of tests could turn up a false positive, concluding that the presumption of guilt of an athlete was 'completely unacceptable.'

Now, however, that study is the subject of intense scrutiny with senior figures at the UCI now understood to be questioning whether it is simply a delaying tactic being used to allow Froome to pursue a fifth Tour title next month.

A key flaw appears to be the admission in the Leiden paper that some of their conclusions are actually based on research not on humans but on dogs. It has actually caused some amusement in UCI circles given the British cyclist's 'Froome Dog' nickname.

Froome was found to have double the permitted limit of the asthma medication in his system

The study states: 'In short, a PK model of salbutamol in dogs was used as the basis and extrapolated to humans using allometric scaling.'

Of further concern when considering the submission of the Leiden paper is the fact that one of the authors of the paper, Adam Cohen, is also the editor of the British Journal of Clinical Pharmacology, and would therefore appear to have influence over whether the research is published in the first place. One of the other authors of the paper, Jules Heuberger, recently published a paper arguing that EPO does not enhance athletic performance.

Publications like the British Journal of Clinical Pharmacology are given 'impact scores' and rankings. The CA-A Cancer Journal For Clinicians is listed as having the highest impact score of 131.72. The publication in which the Leiden paper appeared has an impact score of just 3.83 and was ranked 1193rd in the 2016 list published by Thomson Reuters.

It might explain why WADA's science director, Dr Olivier Rabin, was so dismissive of the Leiden paper last month after it emerged that it was among 1500 pages of scientific material so far submitted by Froome's defence team.

'I read the article you refer to and no, no concern at all,' he said. 'Nothing new as their model is based on three well-known studies.

'We believe the current threshold is solid considering the scientific literature published on Salbutamol over the past 20 years.'