Quote from michael001:
In my case i lost everything that i have in the account, can i claim somewhere the money i lost because the broker didn't execute the margin?
As I said, you need to explain the circumstances and detailed time line in a far more detail.
Just the bare fact that you lost the money and there was a margin call does not entitle you to recover from the broker.
It is like saying, "I had a car accident, can I recover damages from the other driver?" The question cannot be answered until you lay out enough detail to know where fault lies.
You need to explain the time periods involved, what communications there were between you and the broker about the margin call, etc.
If you just sat aside and said nothing after the margin call, that would be the one thing. It is less common now, but there are still a few brokers that give clients 2 or 3 days to meet a margin call and in that case the broker is not at fault if further losses occur in that period.
The literal meaning of "margin call" is a request for additional funds to be added to the account, not necessarily a promise to liquidate immediately.
If you phoned the broker immediately and told him that you would not meet the margin call and asked him to liquidate the trade immediately, and he said he would but actually failed to do so, and further losses were incurred *after* that point, while the markets were open, that would be another different set of circumstances that would be more favorable to you.