Ministers spent less than £4,000 on a bid to recruit an army of ex-teachers to plug Covid staffing gaps in schools, official figures show
Education Secretary Nadhim Zahawi announced the drive last month as he vowed to do "everything in my power to protect education".
But Schools Minister Robin Walker revealed only £3,882.69 was spent on promoting the appeal in answer to a written parliamentary question by the Liberal Democrats.
Early data shows only 485 former teachers have signed up with supply agencies to tackle staff shortages in England's schools.
A further 100 of Teach First alumni - who trained to become teachers through their programme but now work outside the profession - have "expressed an interest".
Teaching unions said the numbers "barely scratch the surface" and are "a drop in the ocean" compared to the challenge caused by the Omicron variant.
It comes as the Department for Education estimate that one in 12 (8.6%) of teachers and school leaders in England - around 44,000 of staff - were absent at the start of term.
Meanwhile, some 4.9% of teachers and school leaders were off school due to Covid on January 6, up from 3% on December 16.
Responding to a written question, Mr Walker said: "As of 5 January, the spend relating to marketing and communications in support of the national appeal for former teachers to return to the profession is £3,882.69."
He said the figures broke down to £1,654.89 on paid search advertising and £2,227.80 for "design work for a toolkit of assets to be used by partners of the department".
Liberal Democrat Education spokesperson Munira Wilson said: "Teacher absences across the country are skyrocketing, yet creating an army of reserves for teachers should have been done 18 months ago before schools reopened.
"To see such a small amount of money spent on getting ex-teachers back into the classroom, at a time of crisis, just proves the Education Secretary's heart’s not in it."
The DfE published the initial data based on a sample of 10% of supply agencies - and said the true figure was likely to be much larger.
Some volunteers may have approached schools directly which was not captured by the figures.
Mr Zahawi said: "Making sure all children and young people can attend school or college remains my number one priority.
"I want to thank all former teachers who have come forward to support the national effort and help keep our children in face-to-face education. I call on all other former teachers who are able to do the same to come forward now.
"The vaccine continues to help us pave the way out of this pandemic and more than ever it is absolutely vital that all those eligible get their booster or second jab, as well as continuing to test regularly."
Shadow Education Secretary Bridget Phillipson said: "These figures show the Government's reliance on the good will of ex-teachers alone is an utterly inadequate answer to staffing shortages, equating to just one additional teacher for every 50 schools."
Geoff Barton, general secretary of the Association of School and College Leaders (ASCL), said he was delighted ex-teachers were coming forward.
But he added: "The numbers quoted by the government barely scratch the surface of the huge level of staff absence caused by Covid-19.
"This initiative, while well-intentioned, was too little, too late, and the government should put more resources and effort into supporting measures to reduce the risk of transmission such as ventilation and testing."
Paul Whiteman, general secretary of school leaders' union NAHT, said: "Unfortunately, the number of former teachers who have returned to classrooms is a drop in the ocean compared to the scale of the challenge faced.
"The latest government figures show that over 40,000 teachers were absent from the workforce in the first week of term."
