UK Transport Minister Grant Shapps has blocked new Covid-19 awareness adverts from appearing on public transport over fears they will deter people from using buses and trains.
Those behind the "Stop Covid Hanging Around" campaign have accused Mr Shapps of undermining their message that good ventilation is essential in enclosed spaces to prevent the spread of the virus.
The "smoke campaign" adverts compare the build-up of Covid particles to cigarette smoke and were signed off by officials from Mr Shapps' own transport department, the health department and the Cabinet Office.
They had been set to be introduced across the public transport network, until Mr Shapps got wind of them.
It was suggested Mr Shapps' objections lay in the fact his department had spent billions of pounds keeping the public transport network open during the pandemic and the adverts could derail the investment.
Allies of the Transport Secretary hit back, however, arguing his concerns stemmed more from the analogy with black smoke than the ventilation theme.
"The instruction to open windows when many buses have sealed windows might confuse passengers. We just want a modification and a rethink," they told The Telegraph.
The dispute isn't the first time Mr Shapps has been at odds with the Department of Health in recent weeks. In October, he contested plans by Health Secretary Sajid Javid to require travellers to film their Covid-19 tests upon returning to the UK.
The latest wrangle came as UK Covid infections fell to their lowest level in five weeks on Sunday night, with 30,305 new cases reported.
Although a hallmark of recent new infections has been their been unpredictable fluctuations, the news provides temporary respite for the government, which has been criticised for the sluggish speed of its booster vaccination programme.
More than 10 million shots have been administered to date, and from Monday about 10 million people aged over 50 will be able to book theirs.
UK Prime Minister Boris Johnson is also expected to confirm this week that all NHS staff must be vaccinated against the virus, although the mandate isn't expected to be imposed until March to avoid a potential mass departure during the busy winter months.