Junior doctors are to go on strike again on three dates, each taking place over 48 hours, the British Medical Association (BMA) said.
The doctors' union also announced that it is to seek a judicial review into the Government's plans to impose new contracts.
The dates planned for industrial action are from 8am on Wednesday March 9 to 8am on Friday March 11, from 8am on Wednesday April 6 to 8am on Friday April 8, and from 8am on Tuesday April 26 to 8am on Thursday April 28.
The strike action will affect emergency care only.
The BMA said it was launching a judicial review after finding that the Government appears to have failed to undertake an Equality Impact Assessment (EIA) prior to its decision to impose a new contract on junior doctors in England.
It said that under the Equality Act 2010, the Government must show "due regard" to equalities issues, typically assessed through an EIA prior to making a decision.
But it added that the Government has failed to provide evidence of an EIA having been conducted ahead of its decision on February 11 to impose a contract on junior doctors from this August.
Dr Johann Malawana, BMA junior doctor committee chair, said: "In recent weeks, I have heard from thousands of junior doctors across the country, and the resounding message is that they cannot and will not accept what the Government is trying to do.
"It now appears that in trying to push through these changes, the Government failed to give proper consideration to the impact this contract could have on junior doctors. This is yet another example of the incompetence which the Government has demonstrated throughout its handling of this dispute.
"Imposing this contract will seriously undermine the ability of the NHS to recruit and retain junior doctors in areas of medicine with the most unsocial hours, where there are already staffing shortages. This will have a significant impact on areas such as emergency medicine, maternity care and paediatrics, to name but a few.
"We have already seen NHS chief executives refusing to support an imposition, and patient representatives have said they are appalled by this move. Added to this, the Government's former adviser on patient safety, Don Berwick, has said it should apologise to junior doctors over the contract dispute.
"The Government must listen to the chorus of concern coming from all quarters and reconsider this disastrous approach.
"The fact is, junior doctors already work around the clock, seven days a week and they do so under their existing contract. If the Government wants more seven-day services then, quite simply, it needs more doctors, nurses and support staff, and the extra investment necessary to deliver them.
"Rather than address these issues head on, the Government wants to introduce a contract that is unfair and in which junior doctors have no confidence.
"The Government can avert this action by re-entering talks with the BMA and addressing the outstanding issues and concerns junior doctors have, rather than simply ignoring them.
"If it pushes ahead with plans to impose a contract that junior doctors have resoundingly rejected we will be left with no option but to take this action.
"The Government must put patients before politics, get back around the table and find a negotiated solution to this dispute."
Just last week medics said they believed a fully-negotiated contract for junior doctors was ''within reach'' as they urged Health Secretary Jeremy Hunt to resume talks over the dispute following weeks of deadlock between the BMA, Government officials and NHS Employers.
The BMA has already staged two walkouts in recent weeks.
The major sticking point has been over weekend pay and whether Saturdays should attract extra ''unsocial'' payments. Currently, 7pm to 7am Monday to Friday and the whole of Saturday and Sunday attract a premium rate of pay for junior doctors.
Under the new contract, 7am to 5pm on Saturdays will be regarded as a normal working day.
Mr Hunt said the new contract will mean an increase in basic salary of 13.5% and that three quarters of doctors will see their take-home pay increase.
Prime Minister David Cameron's official spokeswoman said: "We have been clear throughout discussions with junior doctors that we want to work with them to look at how we bring about a seven-day NHS which we think is in the interests of patients.
"It's regrettable if they are going to strike again. I'm sure discussions with them will continue."