The scheme will see the government top up wages of employees who are working fewer than normal hours due to lower demand within the economy due to the coronavirus.
The chancellor's plan to protect jobs will apply to staff who can work at least a third of their usual hours.
Employers will pay staff for the hours they do work while the government and the employer will each cover one third of the lost pay for the hours' workers don't work.
The grant for the hours that cannot be worked by employees will be capped at £697.92 per month.
Other elements to scheme will see businesses able to apply for 'bounce back' loans and a 15% emergency VAT cut for the tourism and hospitality industries which will now be extended from January next year until March 31.
But controversially Mr Sunak said he was not going to support jobs that were not "viable" and refused to extend the furlough scheme which has kept people employed despite not being able to attend work.
Reacting to the statement, PCS general secretary Mark Serwotka said: "Any support for jobs and key industries during this unprecedented global pandemic is to be welcomed. However, the Chancellor's measures are akin to using a plaster to cover a gaping wound.
"Our members in the commercial sector, aviation and culture are already being threatened with hundreds of redundancies, as employers seek to capitalise on the economic fallout from Covid-19.
"No one should be losing their job due to the coronavirus pandemic and that is why the furlough scheme should be extended.
"The Tories ideological opposition to increased state intervention is hurting the economy and costing people their livelihoods right now."
PCS members in aviation are facing the possibility of hundreds of redundancies and Tate workers are currently on indefinite strike to save over 300 jobs at the prestigious gallery.