Traditional adspend from the top 10 spending brands in the UK plummeted by more than £1.1bn year on year, or 48%, during the height of the coronavirus crisis.
While many advertisers pulled their spend and paused campaigns, the government's health messages took over a lot of space.
As a result, the government was the biggest spender between 23 March and 30 June, with Public Health England spending £43.9m (up 5,000%) and the wider government £15.8m (up 115%) on media, according to the latest figures from Nielsen Ad Intel, which covers TV, radio, out-of-home, press and cinema.
The Scottish government also spent £6.3m – an increase of 540%.
Unilever was the second-biggest spender as its media costs edged up to £29.4m and rival Procter & Gamble was in third place, even though its spend dropped by £6.3m to £27.7m.
McDonald's had the biggest reduction at 97% to £1.4m, having closed all of its restaurants until last month.
The next biggest decline was Sky at £19.1m, down 60%, after sporting events such as the Premier League were postponed, and Amazon, which dropped spend by 77% to £6.5m.
Of those that increased spend, eBay boosted spend to £15.2m (up 176%), followed by streaming service Disney+ at £10.3m (+962%), O2 at £10.8m (+65%) and Microsoft £5.8m (+142%).
Across the different media channels, spend on TV fell 37% to £822.5m, press had a 42% drop to £210.9m, radio was down 34.5% to £151.2m and out-of-home was hit by an 85% decrease to £62.0m. As cinemas closed, there was nothing spent on ads.
However, Nielsen said that the OOH sector almost doubled from £14m in May to £25m in June as lockdown restrictions began to ease. It added that "this was still well below normal levels".
The sectors with the largest cuts were entertainment and leisure at £207m and travel and transport at £138m.
Barney Farmer, UK commercial director at Nielsen, said: "There was no guidebook on how to navigate advertising during the lockdown period, with customers restricted to home environments and an unclear exit strategy. As a result, we have seen varying approaches to advertising, with some increasing spend while the majority cut back.
"Public Health England ran an effective campaign to encourage lockdown compliance and raise awareness of best health practices, and its incredible increase in spend reflects the importance of advertising as a communication platform for any public or private body. As we transition into a less restricted environment, we expect spend to pick up significantly as brands vie to be front of mind."