What do you mean by "ambulance chasers"?

Sorry, it might be an americanism: A lawyer working mostly for profit rather than principle.

#3 definition is probably the closest to common usage: http://www.urbandictionary.com/define.php?term=ambulance%20c...

It's a colloquial term for sleazy lawyer. Specifically, it's a lawyer who seeks out people who were injured, so that they can be that person's lawyer and sue whoever was responsible.