Unions are criticising moves to introduce pay parking for staff at St James's Hospital in Dublin.
Siptu says the move has the potential to cause a strike, and they plan to ballot members.
The Irish Times says staff were told before Christmas they will have to pay up to €500 for their spaces, with the construction of the new National Children's Hospital on the campus.
Siptu says it is unacceptable for management to seek to remove an integral part of staff terms and conditions without any engagement.
Hospital bosses said staff would be charged this year for parking at the site as well as in St James’s Steel nearby.
Staff at the Royal Hospital in Kilmainham face an annual parking charge of €350, but management said that evening and weekend parking would still be free.