In a ballot that closed on Monday, 71 per cent of Unite members and 73.5 per cent of Unison members supported strike action. In addition, 88 per cent of Unite members and 84.9 per cent of Unison members gave their backing to industrial action short of a strike.
Turnout for the ballot was 35 per cent for Unite and 25 per cent for Unison. Unite has more than 400 members at the charity; Unison has 700.
The unions say that Action for Children plans would impose a 1 per cent pay award for 2015/16 with no cost-of-living rise for 40 per cent of its 5,000 employees.
They say that Action for Children also intends to remove contractual pay increments for new starters, refuses to pay the UK living wage of £8.25 – £9.40 in London – and will cut mileage rates on claims for travel expenses.
These claims are not disputed by the charity.
Unite and Unison have argued that, despite the pay reforms, the number of senior executives earning more than £70,000 at the charity has increased from 16 to 21 and another member of staff is on £120,000 a year.
Both unions have called on Action for Children to negotiate through the conciliation service Acas. They have also written to the charity’s celebrity supporters, including the broadcasters Sir Trevor McDonald and Angela Rippon, to seek their support.
Action for Children had an income of £173.1m in the year to 31 March 2015, £6.6m less than in the previous financial year, according to figures on the Charity Commission website. The charity spent £159.9m in 2014/15.
Sir Tony Hawkhead, chief executive of Action for Children, said the charity had "made every effort to reach an agreement".
"We are saddened by the ballot result, which in real terms means that only 5 per cent of staff backed industrial action," he said.
"However, we respect the right of trade union members who choose industrial action. Our top priority is to ensure this has the minimum disruption to our front-line services. Action for Children exists to help the country’s most disadvantaged children and families. We have been working closely with operational managers to put in place contingency plans with the aim of maintaining business as usual for people who depend on our services."
Sally Kosky, national officer at Unite, said: "Staff helping vulnerable families up and down the country have grown increasingly frustrated with management’s high-handed approach. It does nothing for morale and nothing to recognise the invaluable contribution they make day in day out.
"We would urge Action for Children’s management to recognise the strength of feeling and drop its refusal to go to Acas talks, so that we can hammer out a pay deal that properly rewards the hard work of its loyal workforce."
Dave Prentis, general secretary of Unison, said: "Senior managers at Action for Children have acted in a high-handed way by imposing a pay settlement that excludes many staff. Charity workers are dedicated to looking after children and families, and want their employer to see sense and start to listen."