The membership of one of Britain’s largest teaching unions increased by 18,963 last year, figures show.

Figures submitted by the NASUWT to the Certification Office show the number of its contributing members grew from 268,708 at the end of 2019 to 287,671 at the end of the last year - when the Covid pandemic was at its peak.

By contrast, the number of contributing members fell 10,307 between 2018 and 2019.

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As reported by Tes, the union has campaigned for the welfare of teachers during the pandemic, including, in September, when it highlighted how only a third of teachers believed Covid safety measures in their school were adequate.

In November last year it revealed how the pandemic was putting “massive strain on teacher workload”, and in January this year, NASUWT research showed Covid rates for teachers could be up to 333 per cent above average.

The union has also since highlighted the effects of Covid on teacher mental health, and it has called for compensation for teachers who contract long Covid.

The Certification Office says the deadline by which most unions should have submitted annual data was 1 June, however it says it is being lenient this year due to complications caused by the pandemic.

The NASUWT has been contacted for comment on the figures which, at the time of writing, were still to be published on the Certification Office website.