A diplomatic drive in the UK to corner Russia for the Sergei Skripal poisoning has been set back in the past 24 hours, due in part to self-inflicted wounds – notably Boris Johnson’s loose language – but also to Russia’s ability to keep up a relentless counter-propaganda assault that British ministers seem unable to match.

The controversy underlines how rapidly UK intelligence material becomes shop soiled in heated political debates.

The chief executive of the UK’s Defence Science and Technology Laboratory issued a statement saying samples taken from Skripal and his home had been identified as the military-grade nerve agent novichok.

This could have come across as an affirmation of the British position. After all, no country other than Russia is known to have novichok. The idea was to solidify the UK’s case before a meeting of the Organisation for the Prohibition of Chemical Weapons (OPCW) on Wednesday, convened at the request of Russia.

Instead the story emerged as a negative – that UK scientists could not state unequivocally that Russia had been the source of the nerve agent.

Arguably, it was never the expectation that scientists could reach such a level of certainty. The best British position had been always to say that there was no other plausible explanation for the attack other than Russian involvement, either directly or by their failing to control stocks of nerve agent.

Unfortunately for the UK government ministers began to say that overwhelmingly the only explanation was Russian state involvement. In an interview with a German broadcaster, Johnson went further, saying he had personally spoken to scientists at Porton Down and that they had been unequivocal about Russian responsibility.

It is possible the government scientists have now backtracked, at least in public, but Johnson has form in making unforced errors in sensitive foreign policy fields, notably in implying that the British-Iranian dual national Nazanin Zaghari-Ratcliffe was working as a journalist in Iran, rather than on holiday, before she was detained.

In the case of Skripal it seems likely the foreign secretary overstated or misremembered what Porton Down had told him. But in a battle for world opinion, precision matters. Many EU governments, notably Germany, have gone out on a limb with their own public opinion to back Britain’s case against Russia, so it is critical that the British case is coherent and coherently stated.

Russia will also be delighted that on Wednesday morning it spotted a now deleted Foreign Office tweet from last month that attributed responsibility, saying Porton Down had found that the novichok used in the Salisbury attack was definitely “produced in Russia”.

The Foreign Office admitted that the tweet had truncated remarks by the UK ambassador to Russia, Laurie Bristow, and had left a misleading impression.

At one level this episode is trivial but anything that discredits the UK on social media is gold for Moscow.

There has been a second, wider, problem for the UK. Ministers have been forced to wait on the painstaking criminal inquiry in which police, scientists and intelligence agencies cannot produce evidence to order. The OPCW laboratories to which the nerve agent samples were sent need at least another week to complete their work. Scientific research and political rhetoric operate at different velocities.

That has left a vacuum in which Russia, a master of counter-propaganda and sowing doubt, has been relentless. Jean Pascal Zanders, a former chemical weapons project leader at the Stockholm International Peace Research Institute, claims Russia is testing its arguments through social media pickup and has managed to “turn the tables on London”.

On Wednesday Sergei Naryshkin, the director of Russia’s foreign intelligence service, suggested that the Skripal poisoning was a “grotesque provocation rudely staged by the British and US intelligence agencies”.

Even though many of the arguments have been ludicrous, Zanders said they had a cumulative impact designed to depict Russia as a victim. Much of this was for domestic consumption, but was also designed to isolate the UK.

Britain has made something of contradictory Russian explanations, calling them a diversion and saying they are apiece with the way Russia rebutted charges of doping by its athletes and how it denied that the Assad regime was using chemical weapons in Syria.

With a bluntness not normally associated with the diplomatic service, UK diplomats attended a broadcast Russian government briefing on Skripal, effectively challenging the briefer’s bluster on live TV.

It may yet be that the OPCW, as opposed to British scientists, puts Russia back on the defensive by declaring the Salisbury nerve agent was novichok of a kind produced by the Russian state. But the OPCW works cautiously and by consensus.

It may also be the case that police work tracks down passenger records that identify a Russian likely to be responsible for delivering the nerve agent.

But there is a ready audience on the left and the right across Europe, including in the UK, willing to disbelieve the intelligence services in the wake of the Iraq war fiasco or to view the services merely as tools of government.

What seemed like a rapid diplomatic triumph for the UK is emerging over time to be an uphill struggle. For Russia and now the UK, too much of their mutual reputations are at stake to ever concede defeat. This may yet be a long, bruising, struggle in which the evidence gives neither side the vindication they crave.