Ms Glen has already established that, in the two years since the SNP came to power, ministers have made four visits to Ninewells — where members of the public have to pay to park — using official cars.

She is now asking for further details of the visits, including the nature of the trip and whether ministers dodged the £1.70 cost faced by patients, visitors and staff.

But her political opponents are said to have been left vexed by her pursuit of an issue which represented less than £7 worth of parking in two years.

Nonetheless, Dundee West MSP Mr FitzPatrick said he had tabled a question because he wanted to present the “full answer” to the public.

“As Marlyn Glen obviously regards this as a important matter, I have tabled a similar question on free parking for ministerial cars on official business at Ninewells,” he said.

“However, I have asked for the information to be backdated to cover the years from 1999 to the present, so we can have the full answer to present to the public.”

The issue was first raised when the Tele asked health secretary Nicola Sturgeon if she had — like all other visitors to the hospital — paid to park on the site.

The minister neatly dodged the debate, saying she had been dropped off by her official car for the opening of the new radiotherapy suite last month, but there were complaints that it was one law for some and a different one for everyone else.

NHS Tayside has already admitted it makes “special arrangements” for Government ministers’ visits so no parking charges are paid by them.

Most hospitals in Scotland now enjoy free parking, but Ninewells continues to charge because of the cost of terminating the contract of the private company operating the car parks.