I assumed that he is state license and CFP ( certified financial planner ) certified . you can file a lawsuit based on "conflict of interest '" code and others .Seek a lawyer who specialized in fraudulent practices.

It sounds like there is a conflict of interest. Accountant is certainly can be a financual advors, but everything must be in a arm's length.

You will find it hard to prove that he pushes his project to you.
If you have the ability to hire an accountant, the law will assume that you have the knowledge to manage your money.
Anyway, the accountant is unlikely to have a written record of his telling you how good this project is, and that you must invest in it.
I think you just need to take it as a lesson.

If your accountant can prove that he made all the relevant inforamtion available to you and pointed out the risks involved and that he abided by the terms set down by his professional body I am afraid you don't have a leg to stand on.

There is no such thing as a "risk free" investment and this is the first thing all financial planners will tell you when you are thinking of making any investment. Financial planners can only inform you of what could go wrong and make sure you have all the necessary information to make an informed decision. If your accountant did this then he did everything that was expected of him. At the end of the day, you chose to invest in his other business and accept the risks.