Staff at a primary care trust who were overpaid for up to four years have been asked to pay the money back.

NHS Sefton has contacted 350 staff incorrectly paid for working unsocial hours from 2006-10. Staff are to be given up to three years to pay back the money, which totals £160,000 and varies between £20 and £4,500 per individual.

The PCT told HSJ that those being asked to make repayments were all current staff. It will investigate to see whether any former staff were overpaid.

However, Unison regional organiser Paul Summers said many low paid staff would struggle with the “double whammy” of reduced wages from the public sector squeeze and having to pay back £50 or £100 a month.

He said: “We want NHS Sefton to look at the big picture and waive these repayments.

“The law allows them to reclaim the payments but this is at the employers’ discretion.”

NHS Sefton deputy chief executive Marie Rice said the PCT was legally obliged to get the money back.

She said: “We have spoken to all staff affected by this, and we are working closely with their regional union representatives to find a solution that will have the least impact upon them.”

The overpayments were discovered when the PCT changed payroll provider and an audit was carried out. Staff affected include nurses and healthcare assistants.

In 2007, NHS Birmingham East and North told 331 staff it would not seek repayment of an average £600 they were each overpaid due to a payroll error.