HRW has demanded a probe into recent killings and sanctions for those committing them.
The conflict in Darfur entered its sixth year on Tuesday. It has seen the Sudanese army and its Janjawid para-mililtary fighters pitted against opposition forces.
HRW said that in western Darfur "hundreds of civilians" have been killed, tens of thousands have been displaced and provision of "life-saving humanitarian assistance" has been prevented from reaching the worst affected areas by government attacks on villages since February 8.
The rights group said that the UN security council "should strongly denounce" the recent assaults on the villages.
'Darkest days'
Georgette Gagnon, HRW's Africa director, said: "The Sudanese government’s recent attacks take us back to the very darkest days of the conflict.
"The security council shouldn't stand by as though this is "business as usual".
HRW said in a statement that "the council's inaction has given Sudan a green light to continue attacking civilian targets, flouting international law and security council resolutions" and obstructing the deployment of a UN-mandated peacekeeping force.
Gagnon added: "These horrific attacks on civilians show Khartoum's confidence that there will be no real consequences for its actions. It's time for the security council to prove them wrong."
HRW said that a panel of UN experts should be immediately established to look into the attacks in Western Darfur and that those responsible should be held to "targeted sanctions".
EU parliamentarians on Wednesday urged the EU to uphold an arms embargo to China, who they blame for stoking violence via arms exports to the Sudanese government.
The conflict in Darfur has raged since 2003 when anti-government forces attempted to gain a greater regional share of power.
Fighting has claimed 200,000 lives and displaced 2.2 million people, according to UN estimates.