Transport Secretary Grant Shapps has told Sky News claims Boris Johnson's top adviser broke the lockdown twice are "completely untrue".
Dominic Cummings – who was spotted going into Number 10 just before midday – had already admitted that he drove 260 miles from London to Durham with his wife and young son in late March to self-isolate at a family property despite strict restrictions against long-distance journeys.
Now, the Sunday Mirror and The Observer claim the prime minister's right-hand man made a second trip to Durham and was seen there by a member of the public on 19 April – five days after being photographed in Downing Street on his return to Westminster.
Mr Shapps said accusations Mr Cummings "travelled backwards and forwards" are "completely untrue", and since returning to London on 14 April, the PM's most senior adviser had stayed put in the capital.
He told Sophy Ridge on Sunday: "I certainly know that the first one you mention, of travelling back up (to Durham), I know that is not true.
"I'm afraid I don't know (about Barnard Castle) but if that date was true that would have been outside the 14-day period. But I'm afraid I don't have the information on that.
"But I do know it is not the case that he has travelled backwards and forwards, which seemed to be a major part of the stories I saw in the paper today."
More from Politics
Mr Shapps said Mr Cummings was "trying to do his best" by his four-year-old son who was "in danger of having both his parents fall ill".
He said by travelling to Durham, Mr Cummings "took perfectly sensible and rational steps" and "tried to position himself where there was some family support".
"There are all kinds of things that are being said here that are completely untrue," he said.
"The basic story is actually pretty straightforward. Husband and wife were ill, they hunker down, they look after their four-year-old and they don't move until they are better.
"And coming back down to London afterwards, they would have been travelling for essential work which is always allowed as well."
According to Government guidance, households should self-isolate for 14 days if someone in the family has coronavirus symptoms.
Analysis: Govt stance puts at risk public faith in lockdown measures
By Rob Powell, political correspondent
Cracks are beginning to show in the protective ring Number 10 has thrown around Dominic Cummings.
Backbench Tory MPs – some long-time critics of the controversial adviser, some not – are breaking ranks.
The pressure could be insurmountable for Boris Johnson if that overt anger spreads into the cabinet.
Senior scientific advisers, less in hock to the Downing Street machine, may also be worried about eroding their clinical objectivity to placate powerful political figures.
Then there is the risk of public faith in the lockdown measures crumbling.
The government explicitly denied today Mr Cummings made a second trip to Durham.
But the damage may already be done.
Their self-isolate message watered down to protect one unelected but apparently invaluable adviser.
In the latest allegations, Mr Cummings was reportedly spotted by a member of public in Houghall Woods near his parents' Durham home on 19 April.
And a week earlier, the papers allege he was seen in Barnard Castle, 30 miles away from the city, during the period he was believed to be self-isolating.
No photographic evidence has been published, and the reports are based on the testimonies of two eyewitness.
Facing further uncomfortable questions from Ridge abouRead More – Source