Hazard - recalled to the side after being left out of the midweek Champions League win over Schalke for disciplinary reasons - converted after referee Andre Mariner pointed to the spot for what looked like a fair shoulder challenge by Steven Reid on Ramires.
It was rough justice on West Brom, who had looked set for another memorable away victory to add to their success at Manchester United in September after second-half goals from Shane Long and Stephane Sessegnon.
"I am flabbergasted at the decision, I cannot believed the referee gave it," said Clarke.
"What is the point (of talking to the referee)? I cannot change the decision.
"He (Ramires) started going down early before the contact, so you guys can put a label on it if you want.
"For me the onus is on the referee to make the correct decision and he did not make it.
"The referee has to be 100 per cent sure it is a penalty, and how he can be 100 per cent sure in that instance is beyond me. It was a bad decision."
Former Chelsea assistant coach Clarke added: "It is the kind of penalty which can be given when you have got a home crowd which shouts for everything and puts pressure on the referee.
"Referees are human, they can make mistakes like everyone else."
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