The barriers, in St Vincent Lane, were described as "horrendous" and "lethal" by City Mission manager Graham Steven, who believes it is the first time they have appeared in Scotland.
As reported in later editions of last night's Evening Times, the barriers could be forcibly removed by Glasgow City Council, which has not given permission for them. They are believed to have been erected in the past two weeks, next to warm air vents.
Mr Steven said he had been out yesterday to look at the spikes and had been 'saddened' to see them.
He said: "It's not the way to address the issue, it doesn't solve or help anyone. To put spikes down is horrendous. They are pretty lethal."
According to reports, the barriers drove out 29-year-old Gerald, who has reportedly been sleeping rough in Glasgow for the past eight years.
He discovered them after returning from a friend's house in Maryhill.
He said: "When I came back, all the metal had been put down.
"I don't know why they did it. I don't leave it a mess or anything."
He said his friend believed they may have been installed to "make the city look a bit better for the Commonwealth Games," - a suggestion denied by City Mission's manager Mr Steven, who said it was a separate issue.
Mr Steven added: "We have been in meetings with the council about the Games.
"There's always a concern when a big event rolls into town, whether that's Glasgow or elsewhere, that the homeless problem will be swept out.
"[Our chief executive] has been in talks with the council to advise them on how best to deal with it."
Mr Steven added that he believed it was the first time the spikes, which have previously been reported in London, had been installed in Scotland.
Councillor James Adams said the spikes "should not be there" and the local authority would never advocate the use of such a device.
"Regardless of why this structure was put in place, it should not be there," he said.
"We have issued letters to the property owner instructing them to remove it within seven days.
"If they do not then the council will remove it and charge them."