Coronavirus testing in Wales must not become subject to a "postcode lottery", Plaid Cymru politicians have warned.
The party's Welsh Assembly members and MPs in north Wales have written to the health minister claiming patients in the region "appear to be at a particular disadvantage".
They say there are "significant issues" with testing.
Health Minister Vaughan Gething said geography "does not determine the response you get".
"It's important we don't collapse into regional finger-pointing within Wales," he told BBC Radio Wales Breakfast
The letter's signatories include Ynys Môn AM Rhun ap Iorwerth, Arfon AM Siân Gwenllian, North Wales regional AM Llyr Gruffydd, Dwyfor Meirionnydd MP Liz Saville Roberts and Arfon MP Hywel Williams.
'Lack of urgency'
"Not only are we still not carrying out enough tests in Wales, but we are seeing significant issues with tests and the level of testing carried out in the north of Wales specifically," they said in the letter.
"We have been made aware of many instances where possible Covid-19 patients are having to wait extensive periods of time for results to arrive after the tests are initially carried out.
"The Welsh Government must take every conceivable step to make sure that north Wales isn't left behind in tackling this pandemic.
"The people of the north appear to be at a particular disadvantage, and must not become the victims of a postcode lottery - particularly during a time of such unprecedented crisis."
The Welsh Government is planning to be able to carry out between 8,000 and 10,000 Covid-19 tests a day in Wales by mid-May.
In addition to a testing centre which has opened at Cardiff City stadium, Mr Gething said three further facilities would be opened, to include a centre in north Wales.
However, Plaid Cymru's letter claims the timescale shows a "lack of urgency".
Speaking to journalists on Friday, First Minister Mark Drakeford said: "There's no geographical distinction in the way that we process tests.
"Tests get processed all over Wales as fast as we're able to and the results back in the hands of the people who need them.
"Any suggestions that somehow one part of Wales is being disadvantaged in the way things are done, simply isn't true."