The Government has gone back on its pre-election pledge to increase the number of midwives, the Royal College of Midwives (RCM) has said.
RCM general secretary Cathy Warwick said Prime Minister David Cameron and his deputy Nick Clegg had both promised to create more midwifery posts.
But discussions with Health Secretary Andrew Lansley have revealed the Government is "clearly not prepared" to fulfil that commitment, despite the service being close to "cracking point".
Ms Warwick's comments come after an RCM survey found maternity units are facing cuts despite dealing with a high birth rate and more complex deliveries.
About 30% of 83 of the most senior midwives said their units had seen a fall in their budget in the past year while 33% had been asked to cut staff. Two-thirds (67%) of those questioned said they did not have enough staff to cope with demand, despite a high birth rate.
The number of live births in England rose by 107,314 (19%) between 2001 and 2009 to more than 670,000 a year. But the number of NHS midwives rose by just over 2,000 (full-time equivalent posts) over the same period, a rise of 12%.
Ms Warwick told BBC Radio 4's Today programme: "Before the election, both David Cameron and Nick Clegg pledged to (create) more midwives. David Cameron, as recently as January, had an article in The Sun and said if he were in power he would give us 3,000 more midwives.
"What's happened is we have now had a meeting with Andrew Lansley and the Government are clearly not prepared to fulfil that commitment. Midwives have continued to do amazing work despite the fact that the birth rate has gone up by 20% and their numbers have only gone up by 12%."
A Conservative Party spokesman said: "There must of course be enough midwives to meet the demands arising from the number of births. The commitment to 3,000 midwives made in Opposition was dependent on the birth rate increasing as it has done in the recent past. It was not in the coalition agreement because predictions now suggest the birth rate will be stable over the next few years.
"People can be absolutely clear that our commitment to meet the needs of expectant mothers remains, and we will continue to train new midwives to meet the demands arising from the births."