Several Conservative MPs have called for the PM’s chief adviser Dominic Cummings to quit, amid claims he broke coronavirus lockdown rules.
Downing Street says this is “false” and cabinet minister Grant Shapps says Mr Cummings – who has been seen going into No 10 – will not quit.
Steve Baker is among eight backbench MPs to publicly question his position.
Mr Cummings refused to answer questions on the fresh allegations from reporters and TV crews outside his London home on Sunday.
On Saturday, he and the government had said he acted “reasonably and legally” in response to the original claims that he drove 260 miles from London to County Durham with his wife, who had coronavirus symptoms.
Labour has called for an urgent inquiry into the allegations, while government ministers rallied around Mr Cummings on Saturday and defended his conduct.
Matt Hancock and Michael Gove were among those to back Mr Cummings for self-isolating at a property adjacent to other family members in case he and his wife needed help with childcare during the lockdown.
Mr Cummings told reporters outside his home on Saturday that he would not be resigning and had done the “right thing”.
The two newspapers have now reported witnesses saw Mr Cummings in Barnard Castle, more than 25 miles from Durham, on 12 April.
On 14 April, he was seen in London. According to a witness, he was spotted again near Durham in Houghall Woods on 19 April.
Mr Cummings is yet to publicly respond to the new claims, but the Sunday Telegraph reports he told Downing Street he left Durham on 13 April, and that the claim he made a second trip from London was “totally false”.
Transport Secretary Grant Shapps told the BBC’s Andrew Marr that the claims of a second trip was “untrue”.
When asked if Mr Cummings was going to resign, Mr Shapps replied: “No.”
But there are growing calls from backbench Tory MPs for Mr Cummings to consider his position.
‘Position is untenable’
Ex-chairman of the European Research Group (ERG) Steve Baker told the BBC: “The country can’t afford this nonsense, this pantomime, Dominic should go and we should move on and deal with things that matter in people’s lives.”
Tory Sir Roger Gale said there “cannot be one law for the prime minister’s staff and another for everyone else”.
Conservative MP Caroline Nokes tweeted: “There cannot be one rule for most of us and wriggle room for others.”
Colleague Simon Hoare called for Mr Cummings to “consider his position”, Tory MP Damian Collins said the government “would be better without him” and MP Craig Whittaker said Mr Cummings’ position “is untenable”.
Conservative MP Robert Halfon apologised for tweeting his support of Mr Cummings on Saturday and said the PM’s aide should “face the consequences of breaking the law”.
Tory MP George Freeman said a couple taking their child to their grandparents because they have Covid-19 symptoms was not a “sacking offence” but he said it was “time for an apology”.
But Conservative MP Danny Kruger defended Mr Cummings, saying he “made a decision in an emergency” and the prime minister “is satisfied”.
Dominic Cummings allegations: A timeline
16th March – Government tells the UK public they have to isolate for 14 days if someone in their household has symptoms
23 March – Boris Johnson tells the UK public they “must stay at home”
27 March – Dominic Cummings seen leaving No 10
30 March – Downing Street says Mr Cummings is self-isolating with coronavirus symptoms
31 March – Officers from Durham Constabulary “were made aware of reports that an individual had travelled from London to Durham and was present at an address in the city”, the force adds that officers “made contact with the owners of that address”
12 April – According to the Observer and Sunday Mirror, Mr Cummings was seen visiting Barnard Castle, 30 miles from his parents’ residence.
14 April – Mr Cummings is photographed at Downing Street for the first time since 27 March
19 April – This is the date an unnamed witness tells the Observer and Sunday Mirror they saw Mr Cummings in Durham
Labour’s shadow policing minister Sarah Jones told Sky’s Sophy Ridge on Sunday that people “are feeling rightly angry”.
“I think people are rightly feeling is it one rule for us and one rule for people at the top,” she said.
In response to the fresh claims, Downing Street said: “Yesterday the Mirror and Guardian wrote inaccurate stories about Mr Cummings.
“Today they are writing more inaccurate stories including claims that Mr Cummings returned to Durham after returning to work in Downing Street on 14 April.
“We will not waste our time answering a stream of false allegations about Mr Cummings from campaigning newspapers.”
Downing Street has also denied that police spoke to family members of Mr Cummings “about this matter”.
In an updated statement, Durham Police said officers learned of his trip on 31 March and spoke to Mr Cummings’ father the following day.
By Helen Catt, political correspondent
After an apparently co-ordinated show of support from some of the most senior Conservatives yesterday, today the first cracks may be starting to show.
Steve Baker has become the first Tory MP to break ranks and call for Dominic Cummings to go.
As one of Parliament’s most prominent Brexiteers, his intervention is significant.
The tone of his criticism even more so – accusing Mr Cummings of regarding “accountability with contempt”.
His view is that Boris Johnson is expending too much political capital on trying to save his adviser.
The next few hours will see how many more follow suit.
If there’s enough backbench unrest, it will leave Boris Johnson with an unappealing choice to make: oust a highly-valued adviser or risk upsetting the party to keep him.
Other opposition parties have also renewed their calls for the prime minister’s adviser, who masterminded the 2016 Vote Leave campaign, to go.
The SNP’s Ian Blackford said Mr Cummings “has to leave office”, while acting Liberal Democrat leader Sir Ed Davey told BBC Radio 5 Live: “If Dominic Cummings has not been sacked by tomorrow, I think the prime minister’s judgement is in serious doubt.”
Government advice had been for people to stay at home during the first weeks of lockdown. Self-isolation at home continues to be advised for those with coronavirus symptoms.
England’s deputy chief medical officer Dr Jenny Harries said all health guidance should be applied with “common sense”.
It comes as the government announced 282 more people had died with coronavirus since Friday, across all settings, bringing the total to 36,675.