Changing the pay rates of public sector workers, including NHS staff, to reflect regional differences would be an "unworkable, divisive nightmare", union leaders have warned.
Unison said health workers were already suffering a pay freeze, job and budget cuts as well as huge reorganisation in the wake of the Government's controversial health reforms.
In evidence to be submitted on Monday to the NHS pay review body, Unison will say: "The current UK-wide pay system, which sets a floor pay rate for the NHS and allows for adjustments in high cost areas or local areas with particular recruitment difficulties has proven itself as a robust, effective pay system that adequately follows geographic variations in the UK labour market."
The Government is pressing ahead with plans to introduce regional pay in the public sector, sparking union warnings of massive wage cuts for employees in some parts of the country.
Unison, which holds its annual health conference in Brighton this week, said the current pay system, Agenda for Change, took many years to develop and implement and was recognised as the tool to deliver fair pay.
Christina McAnea, Unison's head of health, said: "The Department of Health's evidence on regional pay is built on sand. For a Government that says it wants to cut paperwork, introducing regional pay would be a massively expensive, bureaucratic nightmare, designed to cause huge disruption and conflict.
"Regional pay would cause skills shortages in so-called low cost areas with nurses, midwives and specialised staff being hard to recruit and retain, hitting the care of patients. The Government wants to introduce a market ethos into the NHS but most private companies abandoned regional pay scales years ago as divisive and unworkable."
Andy Burnham, Labour's shadow health secretary, who will address Unison's conference this week, said the Government's plans were "flawed on every level", adding: "First, it fails the economic test, making it harder to control costs and reinforcing the North-South divide.
"Second, it fails the heath policy test. Differential pay will bring instability to the NHS, with the risk of one area poaching staff from another. It makes it harder to bring the best staff to the more deprived parts of the country where the health challenge is often greatest."
A Department of Health spokesman said: "Our evidence shows how more market facing pay could help employers make better use of the NHS pay bill. It makes clear that there is a compelling case for implementing market facing pay for all Agenda for Change staff in England, whether they fulfil a support role, work in administration or work on the front line such as nurses and other clinical staff. The principle of equal pay applies to all staff across the entire country."