The firm's managing director, Mr Christophe Audergon, was quoted as saying: "Crossinvest does not condone the comments. We believe they were made in poor taste."
On Tuesday, Mr Casey, 39, who is married to former Miss Singapore Universe Bernice Wong, apologised in a statement for having "offended and disrespected the people of Singapore".
"I wish for nothing more than to be forgiven for my poor judgment and given a second chance to rebuild the trust people have had in me as a resident of this wonderful country," said the permanent resident.
This came after two of his Facebook posts began circulating on the Internet. In one, a picture of his five-year-old son on an MRT train was accompanied by the caption: "Daddy where is your car & who are all these poor people?"
In the other post, his son is pictured in a silver Porsche with the comment: "...Normal service can resume, once I have washed the stench of public transport off me..."
A YouTube video of Mr Casey was later posted in what seemed like a taunting response to his detractors, but he said in his statement that this was a "misuse of an old video by unknown sources".
Mr Casey also said his family had suffered "extreme emotional and verbal abuse online" and had even received death threats.
Many readers of The Guardian's left comments on its site condemning Mr Casey's actions. "There are a number of these British prats in Singapore working in the financial sector. They think they are God's chosen few but in reality despised by the many. Remember Nick Leeson?" wrote reader ThaiPete.
One defended the cleanliness of Singapore's public transport.
Happy Valley wrote: "Singapore actually has the cleanest public transport system I have ever used. In fact Singapore is clean all round. I believe that it is the only country in the world that bans chewing gum. This guy is a total and utter git. Biting the hand that feeds him. He deserves to be kicked out."
In its report, The Telegraph quoted an unnamed male expatriate who supposedly knows Mr Casey and his family. The expatriate said that Mr Casey "has a very British sense of humour, which can be very scathing".
"It can cross lines and it did cross lines. I had to defriend him on Facebook because I couldn't stand the rubbish he was writing about all sorts of people. However, his wife and son were sweet," he was quoted as saying.
