Junior doctors are considering further strikes in September after rejecting Health Secretary Jeremy Hunt's proposed new contract.
Ellen McCourt, who chairs the British Medical Association's (BMA) junior doctors committee (JDC), said that by "standing together" they could demand the Government takes them seriously.
Strikes took place between January and April after junior doctors failed to come to an agreement with the Government over a proposed new contract.
In July, the Government announced it would impose a new contract after junior doctors and medical students voted to reject a contract brokered with the British Medical Association (BMA).
In a letter to members released on Twitter on Thursday night, Ms McCourt said that the Government had remained "persistently silent" on the issues she said had led to the rejection of the contract.
She said: "In light of this, the JDC Executive has voted to reject the proposed new contract in full and to call for formal re-negotiations on all of your concerns.
"In response to the Government's silence, JDC exec has today made a formal request for a special meeting of BMA Council to authorise a rolling programme of escalated industrial action beginning in early September."
She said the BMA could not "stand idly by" as the date for imposition drew nearer, saying that forcing a contract on doctors that they did not have confidence in would be bad for patients.
She added: "The road ahead will not be easy, but together we can demonstrate our commitment to securing a contract that is acceptable to junior doctors; by standing together we speak with one voice and demand the Government takes us seriously.
"Our unity remains our strength."