The study from Speech and Language UK said at least 1.7 million children were struggling with verbal communication and it risked impacting their education.
The researchers asked British primary and secondary school teachers about the impact the pandemic had on their pupil's ability to talk and understand words.
Jane Harris, Speech and Language UK Chief Executive said the study was a "wake up call" for the government.
She said: "Our education system has failed to recognise that some children struggle to learn to talk and understand words, just as some struggle with reading, writing and maths."
The negative impacts of the Covid pandemic on education has been well documented and the government has been criticised for not going far enough to address the situation.
Research carried out in 2021 by the Early Years Alliance found three in five early years workers believed fewer pupils were entering education with the necessary learning development and even play skills to succeed.
Former Prime Minister Boris Johnson pledged £3.1 billion of catch-up funding available in England to help children who faced disruption to their education due to Covid-19.
But this was far below the £15 billion recommended by the government's education commissioner for England Sir Kevan Collins who resigned in protest at the funding.
A Department for Education spokesperson said: "We are investing nearly £5 billion to help children and young people recover from the impact of the pandemic, which includes targeted support for the pupils who need it most through our flagship National Tutoring Programme - with over two million high quality tutoring courses already started.
"We are also investing £24 million in building children’s literacy and speaking skills as part of our ambition for 90% of children to leave primary school reaching the expected standard in reading, writing and maths by 2030."
Speech and Language UK said their research found the figures had increased by 200,000 since they conducted a similar study last year.
They found 72% of teachers surveyed believe students transitioning from Year 6 to Year 7 will struggle more with their speech and language in comparison to year groups who started secondary school before the coronavirus pandemic.
The study also noted 41% of teachers feel they do not have enough training to support pupils who are behind with their language skills.
Speech and Language UK said addressing the issue should be a priority for the government and called on them to create free resources to help pupils catch up and provide extra training for teachers.
The government does have several programmes to help children who are falling behind in their speech and literacy.
On Monday the government announced a further £24 million to help tackle the issue.
They said the government was committed to the target of 90% of primary children reaching the expected standard in literacy and numeracy.
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