A computer glitch means that cornavirurs cases recorded in the last week in Wales could double after 11,000 were missed from the original figures.
Currently, recorded figures for the country for the week of December 9-15 stand at 11,911.
But Public Health Wales (PHW) says a further 11,000 extra cases were missed because of a ‘planned maintenance’ of some IT systems.
The computer problems are thought to relate to tests processed in ‘lighthouse labs’.
A total of 103,098 people have tested positive in Wales since the Covid crisis began, meaning the 11,000 extra positives – which will be added PHW figures on Thursday – will represent roughly one tenth of the new total.
Plaid Cymru health spokesman Rhun ap Iorwerth told the broadcaster: ‘With positive cases in Wales rising to record levels it is crucial that the reporting of data is both timely and robust.
‘The public need a complete and current picture of the situation to realise the gravity of what we are facing.
‘We need urgent reassurance that the failings have been addressed.’
Yesterday, it was reported that 30 more people had died with coronavirus in Wales and 530 more cases were announced.
It comes as cases continue to rise in the country with First Minister Mark Drakeford announcing a tightening of the Christmas bubbles rules and a third lockdown from December 28.
In a dramatic break with the UK-wide approach, Mr Drakeford will change the law so just two households can mix rather than three.
He also said the nation would go back into lockdown once the five-day Christmas relaxation of rules is over.
Wales currently has the highest infection rate in the UK – 425 per 100,000 people – with eight of the top ten worst-hit areas.
Mark Drakeford said today that Wales would be going back into lockdown once a relaxation of rules over Christmas comes to an end
Mr Drakeford said one in five people in Wales is testing positive for the virus, while more than 2,100 are in hospital with symptoms. A record 98 are in intensive care.
Wales only ended a 17-day ‘firebreak’ lockdown on November 8.
Mr Drakeford said new measures were necessary because the situation had become ‘so serious’. He stressed that the ‘sustained rise in coronavirus’ meant the country would go into its third lockdown from Monday December 28.
Non-essential shops and gyms will close earlier – on the evening of Christmas Eve – while all restaurants, pubs and bars will shut from 6pm on Christmas Day. From December 28, tighter rules will restrict household mixing, travel and holiday accommodation.
Mr Drakeford said Wales’s move into the fourth and highest level of restrictions would last for three weeks before being reviewed. He insisted: ‘The situation we are facing is extremely serious.
Non-essential shops and gyms will close earlier – on the evening of Christmas Eve – while all restaurants, pubs and bars will shut from 6pm on Christmas Day. From December 28, tighter rules will restrict household mixing, travel and holiday accommodation
Christmas advice has toughened up in Wales, with Mr Drakeford changing the law so that no more than two households can mix. He said: ‘A shorter Christmas is a safer Christmas’
‘We must move to alert level four and tighten the restrictions to control the spread of coronavirus and save lives.’
The First Minister also toughened up the Christmas advice, changing the law so that no more than two households can mix.
He said: ‘A shorter Christmas is a safer Christmas.’
The Welsh government later said that the guidance on two households would be enshrined in law.
Matthew Jones, clinical director for emergency care at the Prince of Wales hospital, told ITV that ambulances were queuing outside with patients.
He said: ‘With the ambulances outside like this, there’s a strong argument that we are beyond crisis point – that this isn’t safe.’