Potential drugs cheats are "strongly mistaken" if they think they can get away with doping while there is reduced testing because of coronavirus, the head of UK Anti-Doping has warned.
Nicole Sapstead, chief executive of the national agency, said it would be "naive" for athletes and coaches to think they would leave no trace of their activity.
Ukad announced it had significantly scaled back its programme of testing during the coronavirus pandemic, which has so far claimed 33,000 lives.
Some countries, including Russia and Canada, have stopped testing completely.
Last week Travis Tygart, head of US Anti-Doping (Usada), said the situation opened a "window of opportunity" for those not "willing to compete clean".
However, Sapstead said the agency would "come after" anyone looking to break the rules while they thought they were "off the radar".
She told BBC Sport: "There will always be a minority that will seek to dope, and whether that is now, when they think they are effectively off the radar of national anti-doping organisations, or at any other time, my message to them is very, very clear - we will continue to process intelligence, we will continue to monitor whereabouts, we will continue to monitor the raft of information we have available to us, such as the athlete biological passports.
"All of this helps us to gain a picture of what an athlete might be doing during this time. And if they think they are going to get away with it then they are strongly, strongly mistaken.
"And at the time when anti-doping organisations start to ramp up their activity again, we will come after them."
It is understood Ukad is still carrying out some urine testing.
However, the shutdown of domestic sport has meant there is no in-competition testing, and the number of out-of-competition tests has been cut back.
Sapstead continued: "Obviously it is problematic now with a reduction in testing.
"And who knows how the coming weeks may play out? Clearly we are going to have to be mindful of the advice that is coming out of government and be respectful of that at all times."
Sasptead said that when global sport resumed after the coronavirus pandemic there would need to be a drive to "plug the gap" in testing, in order for sport to maintain its integrity.
But she said she "would like to think" the postponed Tokyo 2020 Olympics and Paralympics could be cleaner than any Games before.
Ukad recently criticised UK Athletics (UKA) for not releasing the outcome of its 2015 review into how it handled its relationship with Mo Farah's disgraced former running coach Alberto Salazar, despite "repeated" requests. UKA said it was "inaccurate" to suggest it had been obstructive.
Sapstead confirmed that there are ongoing discussions with UKA's legal team on the matter.
"Our lawyers have been in touch with their lawyers and we are working through it now," she said.