LONDON -- British Prime Minister Boris Johnson refused Wednesday to hold an official inquiry into the actions of his closest adviser for allegedly flouting COVID-19 lockdown rules, imploring an angry public to move on from the scandal rocking his government.

Facing questioning by Parliament's Liaison Committee of senior lawmakers, Johnson said an inquiry wouldn't be "a very good use of official time."

"We're working flat out on coronavirus," he said.

Opposition politicians have written to the head of the civil service asking for an investigation into Johnson's top aide, Dominic Cummings.

Cummings drove 250 miles (400 kilometres) from London to his parents' house in northeast England while he was falling ill with suspected COVID-19 -- despite stay-at-home rules that the government had imposed on the rest of the country.

Cummings says he travelled to the family farm so that his nieces could care for his 4-year-old son if he and his wife both became sick. But that explanation has prompted fury with many Britons, who say they were unable to attend funerals and visit elderly relatives, among other struggles, in order to follow government advice at the time to "Stay Home ... Save Lives."

Johnson, who was himself hospitalized with COVID-19 last month, has said Cummings "followed the instincts of every father and every parent."

After days of public outrage over double standards, the government sought desperately to change the subject.

"I think what we need to do really is to move on," Johnson said, telling critical lawmakers to "lay aside party political point scoring."

"I totally understand public indignation, I totally understand that, but I do think that ... it would be much better if we could now move on and focus on the next steps."

But anger at Cummings has gone well beyond partisan politics. At least 30 lawmakers in Johnson's Conservative Party have called on Cummings to resign, citing an outpouring of fury from their constituents.

One senior lawmaker on the Liaison Committee, former Health Secretary Jeremy Hunt has already said Cummings broke the rules. Another, Women and Equalities Committee chairwoman Caroline Nokes, said "there cannot be one rule for most of us and wriggle room for others."

But Johnson appears determined to retain the aide seen as instrumental to his rise to power -- even if it erodes public trust in Britain's response to the pandemic.

The scandal is particularly damaging because it comes as Britain is slowly beginning to lift lockdown restrictions.

Johnson confirmed that a national "test and trace" program would start work Thursday. About 25,000 people have been hired to track down the contacts of anyone who tests positive for COVID-19 and ask them to quarantine themselves for 14 days. The goal is to isolate the sick before they spread the virus to anyone else.

The plan is considered essential to Britain's efforts to ease lockdown and return to normality after an outbreak that has been one of the world's worst. Britain's official coronavirus death toll stands at 37,460, the highest total in the world after the United States.

Johnson said the track-and-trace program would mean a "big imposition" on a small minority, for the good of the whole country.

"That is the tool that other countries have used to unlock the prison" of lockdown, he said.