Plans to stop operations being performed at a children's heart centre are a "scandal of national proportions", a union has said.
Unite said that the proposals to end heart surgery at Leicester's Glenfield Children's Heart Centre were "penny pinching".
In July, NHS England announced that the number of hospitals in England allowed to perform children's heart surgery is to be cut in a controversial move.
Under the plans, 13 "level 1" centres that perform surgery will be cut to 10, and nine "level 2" specialist cardiac centres will be cut to four.
Some NHS trusts said they would fight the decision, with Leicester saying it would not sit by while officials at NHS England "destroy our fabulous service".
It said its results were among the best in the country and that closing its service would threaten other key children's services in the region, including intensive care.
Unite, which has organised a protest in Leicester on Saturday, said that the proposals were not based on empirical evidence.
Sarah Carpenter, Unite's national officer for health - who will be addressing the rally, said: "There is no logic or empirical evidence to close this first-class centre and force very sick children to seek treatment in Birmingham and possibly even further away.
"This is a cruel proposal which is completely unnecessary - this is a scandal of national proportions, where penny pinching trumps great care for children born with heart defects.
"We call on the people of Leicester to turn out in their thousands for Saturday's rally."
Officials at NHS England believe that while units in England are safe, not all are providing excellent care.
In July, when the proposals were announced, officials said they hope that by centralising services, outcomes for patients will continue to improve - with more patients surviving and those children born with congenital heart defects living longer into adulthood.
The changes are due to be brought in from April next year.
Congenital heart disease services have been the subject of a number of reviews since the public inquiry at Bristol Royal Infirmary in 2001.