The NHS Confederation has questioned the legitimacy of next month’s planned NHS strike after it emerged that just 16 per cent of Unison members took part in the vote.

Thousands of NHS staff are due to walk out for four hours on 13 October between 7am and 11am following a dispute with the government over pay - the first time unions have taken industrial action over pay in 32 years.

While Unison refused to reveal the ballot turnout when announcing the ballot result last week, figures seen by HSJ reveal that the union received just 40,104 votes after polling 250,000 NHS members, representing a turnout of 16 per cent.

Rob Webster, chief executive of the NHS Confederation, said: “The proposed action will inevitably delay many treatments and distress thousands of patients, and we would ask them to question whether it’s right to do so where a ballot turnout is low.

“It’s essential any unions planning to join the strike coordinate closely with employers right now, well ahead of the mandatory seven days minimum notice, so that hospitals and other health providers can start planning care.”

Unison head of health Christina McAnea admitted she was disappointed with the turnout.

“We know that health members, whilst they are angry and demoralised, are reluctant to take industrial action because they worry about the impact it would have on patients,” she said.

“We think many more people will go out on strike than took part in the vote because of the loyalty to the union, and we will be taking this action in partnership with other unions.

“What is shocking is that the government knows the NHS workforce don’t want to take strike action, but they have engineered this situation and left us in a position where we have had no choice but to seek our members views.”

She said unions were hampered in ballots by being forced to use postal votes because ministers refuse to allow electronic or secure telephone voting.

The dispute focuses on the government’s decision to reject the independent pay review body report earlier this year which called for a 1 per cent pay rise for all staff. Instead those at the top of their pay band will receive a non-consolidated, non-pensionable, pay rise of 1 per cent.

The government has offered unions a deal on pay but only if they agree a freeze on incremental pay in 2015-16.

The strike will be followed by four days of action short of strike action between 14 and 17 October when members will stop working through breaks.

Nine more unions including Unite and the Royal College of Midwives are balloting for strike action with the health service facing the prospect of ongoing action throughout the autumn.

The Royal College of Nursing is not balloting members on industrial action.