UN humanitarian chief Valerie Amos told the council that 9.3 million people now need outside help to survive, up from 6.8 million in September, and 6.5 million are now homeless inside the country, up from 4.25 million.
The United Nations estimates more than 2.2 million people have fled to neighboring countries and the figure will be above three million by the end of the year.
With neighboring countries such as Jordan warning that they cannot cope with the influx, Amos appealed to the council for its "help and influence" to press for greater access to give assistance inside Syria.
Amos said the council "should put its full political weight with both the government and the opposition parties" to ensure that previous calls for access are carried out, Britain's UN ambassador Mark Lyall Grant said after Amos gave a private briefing to the council.
The humanitarian chief handed the council a letter which set out a call for greater pressure to back a statement agreed by the Security Council on October 2 calling on the government and opposition militants to make it easier to provide food and medicines, diplomats said.
Amos told the council that the Syria crisis "continues to deteriorate rapidly and inexorably," said her spokeswoman Amanda Pitt.
The 15-nation council is divided over the 32-month-old war which the UN says has left well over 100,000 dead.
The war in Syria started in March 2011, when pro-reform protests turned into a massive insurgency following the intervention of Western and regional states.
The unrest, which took in terrorist groups from across Europe, the Middle East and North Africa, has transpired as one of the bloodiest conflicts in recent history.