Technology has left many Britons unable to spell words like "definitely" and "separate", a survey has found.
It suggests that the UK has produced an "auto-correct generation" that relies on computer spell checks.
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 common 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 this all the time, while a further 21% said they rely on it 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."
he engines of the SpaceX Falcon 9 light but fail to launch from the Cape Canaveral Air Force Station on May 19, 2012 in Titusville, Florida. The launch in the early hours of Saturday morning would have made SpaceX the first commercial company to send a spacecraft to the International Space Station. (Photo by Roberto Gonzalez/Getty Images)
Chelsea Pensioners open the Westland Magical Tower Garden, a 24 meter high seven-tiered garden display, at the RHS Chelsea Flower Show, in Chelsea, west London.(PA)
will.i.am passes the Olympic Flame to torchbearer Emma Folwer in Taunton, Somerset.(PA)
The Prince of Wales watches as the Duchess of Cornwall tastes a sponge cake at the St-Francis School in Saint John eastern Canada, on the second day of a four day Diamond Jubilee tour of the north American country.(PA)
Visitors wait in front of the entrance of the Tokyo Skytree in Tokyo, Tuesday, May 22, 2012. The world's tallest tower and Japan's biggest new landmark opened to the public on Tuesday. (AP Photo/Itsuo Inouye)
Workers put finishing touches on the carving wax featuring Lord Buddha during the preparation to celebrate the 2,600 years of Buddhism in Bangkok, Thailand Tuesday, May 22, 2012. (AP Photo/Apichart Weerawong)
An aerial view of the Mosquitia region near the remote community of Ahuas, Honduras, Monday, May 21, 2012. On Friday May 11, a joint Honduran-U.S. drug raid, on a helicopter mission with advisers from the DEA, appears to have mistakenly targeted civilians in the remote jungle area, killing four riverboat passengers and injuring four others. Later, according to villagers, Honduran police narcotics forces and men speaking English spent hours searching the small town of Ahuas for a suspected drug trafficker.(AP Photo/Rodrigo Abd)
Niagara Falls emergency officials rescue a man who plunged over Niagara Falls and survived in an apparent suicide attempt, Monday, May 21, 2012. The man is only the third person known to have gone over without a safety device and live. A waiting helicopter flew him to Hamilton General Hospital, where a spokeswoman says he has critical but non-life-threatening injuries. (AP Photo/Harry Rossetani)
An Iraqi man rides his donkey cart in a Baghdad street, in a yellow haze from a heavy dust storm which shut the capital's airport on May 22, 2012. AFP PHOTO/SABAH ARAR (Photo credit should read SABAH ARAR/AFP/GettyImages)