Computer auto-correct technology has left many British adults unable to spell simple words such as "definitely" and "separate", a Mencap survey has found.
The research suggests that the UK has produced an "auto-correct generation" that relies on spell checks to get common words right.
The poll, which questioned more than 2,000 adults, found that around a third could not spell "definitely", while a similar proportion failed to pick the right spelling of "separate".
And around two-thirds (65%) picked a wrong spelling for "necessary" from a list that did not include the right spelling.
But while many adults struggle to spell these simple words, the poll also found that three-quarters of those questioned (76%) think they are good at spelling, with 96% saying that spelling is important.
And many people are relying on spell checks - 18% said they use one all the time, while a further 21% said they rely on them most of the time. Fewer than one in 10 (9%) said they never use a spell check.
The survey was commissioned to mark Mencap's Spellathon Championships, which take place this week.
Mencap chief executive Mark Goldring said: "With over two-thirds of Britons now having to rely on spell check, we are heading towards an auto-correct generation.
"This survey has highlighted that many Britons have a false impression about their spelling ability.
"Today's tough economic climate means that poor spelling on a CV is fatal, as it says that an individual cannot produce work to a given standard, no matter how highly qualified they might be.
"Language used by a company or person is a reflection of their attitude, capabilities and skill."