Wales NHS scan and ultrasound waiting times treble
The number of patients waiting longer than they should for diagnostic services like MRI scans and ultrasounds has trebled in the last two years.
Figures also show proportionately more patients in Wales face waits of over eight weeks than in England.
The Welsh government said health boards were working to address backlog issues.
The number of people waiting more than nine months for hospital treatment in Wales has also reached its highest level in two years.
When a patient is referred for diagnostic services such as a CT scan or an endoscopy they are meant to be seen within eight weeks - the so-called "operational standard".
But according to the figures for November 2013, more than 23,500 were left waiting longer - up from just under 8,000 two years ago.
BBC Wales analysis on statistics also show 32% of patients in Wales waited longer than eight weeks for an ultrasound scan compared with 0.1% in England whose figures were released on Tuesday.
And for CT scans, 7.5% of patients in Wales were waiting more than eight weeks whereas the figure for England is 0.07%.
Cathy O'Sullivan, acting director of the board of Community Health Councils in Wales which represents patients, told BBC Radio Wales: "The system is not working in the best interest of patients.
"It needs a very fundamental shake around how patients are treated in the 21st Century."
Shadow Conservative health spokesman Darren Millar AM called for the Welsh government to invest more in NHS frontline services.
"It looks as though the National Health Service is turning into something of a national waiting service," he said.
On Thursday, statistics on referral to treatment times showed that the number of patients waiting longer than nine months for hospital treatment in Wales had hit a new high.
Numbers rose to 13,269 people at the end of November - an increase of about 1,000 on the previous month and nearly 8,000 since March 2013.
The Welsh government's target is to treat all patients within nine months.
Official figures also highlighted 88% of people waited less than 26 weeks to start treatment. The target is 95%.
Health Minister Mark Drakeford said the Welsh NHS was "under pressure" but stressed it was not "in crisis".
He told BBC Wales: "There are fewer people waiting overall in the Welsh NHS than before.
"The number of people waiting over 26 weeks has come down but I am disappointed to see the rise in people waiting over 36 weeks.
"I've made it clear to local health boards, even in the difficult period over the winter, I expect them to concentrate on those longer waiters and I do expect to see those figures coming down."
Thursday's figures drew criticism from opposition parties in Wales with the Conservatives describing the situation as an "increasingly worsening crisis".
The Liberal Democrats called the figures "disgraceful" and Plaid Cymru said they were a "predictable result of health boards not scheduling surgery over the winter months".
In a response to the McGivern family, a Betsi Cadwaladr University Health Board spokesperson said: "We aim to see all patients referred for this type of scan within eight weeks of referral and we are very sorry that Amy had to wait so long to be seen.
"Due to increasing demands on the service - with referrals for the Wrexham service increasing by 13% this year - for some patients, waiting times have increased.
"To tackle this, we have invested in additional MRI capacity in the Wrexham area and have scanned an additional 380 patients during December. In addition to this, we plan to scan a further 420 patients before the end of March, with the aim of reducing the typical waiting time to the target of eight weeks."
A Welsh government spokesperson said: "Work is already under way to tackle the rise in the number of patients waiting longer than eight weeks, with health boards putting in place a number of measures such as the use of mobile MRI scanners.
"We would expect to see improvements in the length of wait between now and the summer. This will be linked to the three-year plans that are due in the end of this month, and also to the planned care work programme.
"The increase in waiting times for diagnostic services has been caused by a rise in demand for services such as scans and endoscopies to help diagnose cancer.
"Further action to speed up access to diagnostic services will form part of the programme of work announced by the health minister before Christmas to develop sustainable improvement in planned care performance."