The hunt for an unidentified person who tested positive for the Brazil variant of coronavirus has narrowed to 379 households in southeast England, the health secretary has said.

In total, six cases of the P1 coronavirus variant first found in Brazil have been discovered in the UK.

One has still yet to be identified after the individual failed to complete their test registration card.

But Matt Hancock told the House of Commons on Tuesday that officials had now "identified the batch of home test kits in question".

He added: "Our search has narrowed from the whole country down to 379 households in the southeast of England and we're contacting each one.

"We're grateful that a number of potential cases have come forward following the call that we put out over the weekend."

There are concerns that the Brazil variant may spread more easily, might evade the immune system, or that vaccines might be less effective against it.

Mr Hancock said the UK's current vaccines had "not yet been studied against this variant" but that work is under way to "understand what impact it might have".

"We do know this variant has caused significant challenges in Brazil," he added.

"So we're doing all we can to stop the spread of this new variant in the UK, to analyse its effects and to develop an updated vaccine that works on all these variants of concern and protect the progress we've made as a nation."

The health secretary also told MPs there "may well be a need" for people in the UK to receive a third vaccine dose in the autumn in order to combat variants.

Of the five other cases of the Brazil variant in the UK, two have been identified in south Gloucestershire and three in Scotland.

All five of the identified cases are linked to travel from Brazil to the UK.

Labour's shadow health secretary, Jonathan Ashworth, suggested the unidentified person had "vanished into thin air" as he called for a strengthening of the test and trace programme.

"How on earth can a test be processed that doesn't collect the contact details?," he asked.

"And what mechanisms will be put in place to fix this in the future, because £22bn has been allocated to this system - it feels to me that somebody has vanished into thin air."

Mr Ashworth said it was "obvious that tougher border controls should have been in place sooner" to prevent the import of COVID variants from abroad.