This newspaper's investigation revealed that diagnostic samples and test results were being exchanged on the side of a walkway off Dartmouth Square in Ranelagh.

Residents of the upmarket square, who were already embroiled in controversy over the closure of the square's park, were furious that the adjoining Dartmouth Road was being used by Claymon Laboratories in this way.

Having monitored the activities of Claymon's logistics vehicles in the area for several weeks, the Sunday Tribune witnessed drivers take boxes, envelopes and other items out of their vans and place them on footpath as they exchanged the materials a fortnight ago.

A spokesman for Claymon Laboratories this weekend said: "No exchanges have been made on Dartmouth Road for a number of weeks now. We are using an alternative facility and the footpaths in Dartmouth Road were only being used as an interim measure."

Claymon Laboratories carries out a range of clinical tests, including blood-test analysis, cervical smear test analysis, urinalysis and viral screening.

The company's website reveals it is also subcontracted to work for the Health Service Executive and the prison service.

A spokeswoman for the Irish Prison Service confirmed that their urinalysis tests, used to check for drugs, are carried out by Claymon and the contract includes a clause that Claymon "secure the safe transfer of the samples".

This weekend, the spokeswoman said: "After the story appeared in the Sunday Tribune, we contacted Claymon Laboratories and were given an assurance that our samples are transferred from prisons to their laboratories on a point-to-point basis with no transfers in between."

A HSE spokesman said, "The HSE expects that all its diagnostic samples being transported are done so in the most secure way possible."

In response to the original investigation, a spokesman for Claymon said: "There is a serious traffic problem in Dublin and rather than having each van drive to seven or eight hospitals across Dublin, it is better to have a centralised spot for them to meet and exchange the materials for a short time."