A British woman desperate to return home says the Government's flawed ticketing system for managed isolation facilities could cost her $5000 and means she won't see her ill dad before he dies.

Halide Way is just one of a number of Kiwis who have contacted the Herald with complaints about the system being oversubscribed, not being able to get through to the call centre and having issues with the website not showing the availability calendar at times.

The latest complaints come a day after Prime Minister Jacinda Ardern defended the stretched system and pleaded for anyone with a MIQ voucher and who would not be using it over Christmas to let officials know so space could be freed up.

The 49-year-old, whose father is in the advanced stage of Parkinson's Disease and can no longer speak or type, has been trying for months to get back to the UK so she and her children can see him one last time.

She has already had two trips cancelled on her earlier in the year due to flights being stopped and now fears her latest attempt to take the children home for Christmas may also be scuppered as she cannot secure a spot in a managed isolation facility for her return date.

Way booked the latest flights in July for $5000 and since learning about the new managed isolation allocation booking system at the start of October has been checking the website every day looking for her date to become available.

After MBIE last week warned people wanting to come home before Christmas that dates were filling up fast, she started checking the booking website three to four times a day.

She also contacted MBIE via its Facebook page last week and was told the date she was after - January 16 - would not be released until mid this week.

But on Sunday the first spots for the date were released and were taken within two hours.

Last night she also set her alarm for every three hours so she could check whether a space was available.

Way said the new system was extremely stressful and did not make any allowances for people who had booked their tickets prior to the ticketing system being sprung on them.

"I now have $5000 worth of flights that I bought in good faith, that I cannot use, but more importantly, there is now a very real chance that I will not get to see my dad before he dies."

After splitting up with her Kiwi husband not long after relocating to New Zealand at the end of last year she felt cut off from her support networks and immediate family.

"It feels like there's no easy way out. I would never have come if I didn't think there was a possibility that I couldn't just nip on a plane if something happened.

"We could be on the moon in New Zealand at the moment."

She estimated she had spent $23,000 on flights home and was still waiting for refunds, so could not purchase any more flights.

She had also looked at changing her flights but said the airline didn't always fly on the available dates, while others were charging exorbitant fares.

Not only had she planned her trip to make sure she would be home in time for her children aged 7 and 9 to complete isolation before starting school, but she also had a shared custody arrangement with her ex husband to follow so taking a chance on a spot becoming available was too risky, she said.

She had also been given the incorrect information about when her dates would be released when she contacted MBIE via the FB page, so missed the first release. The next available spot, as of Monday afternoon, was February 8.

Way knew she wasn't the only one being put under such stress from the country's strict system and feared it would have a negative impact on people's mental health.

A Managed Isolation and Quarantine spokesperson acknowledged there were many people in heartbreaking situations as a result of this global pandemic, but isolation was an important part of the Government's border measures to keep Covid-19 out of New Zealand.

"The reality is that there is finite capacity within the MIQ system. New Zealanders can still come home but possibly not on the dates they would prefer."

A small number of places did become available from time to time if people cancelled their vouchers so people should check regularly to see if space has opened up on their preferred dates, they said.

A dedicated service desk team had also been set up to handle queries from returning New Zealanders. Since the ticketing system launched on October 5, 36,537 passengers have secured an allocation to a Managed Isolation Facility.