Bowel cancer diagnosis rose 12% as a result of GP referrals during the Be Clear On Cancer campaign in England in 2012, according to joint organisers Cancer Research UK.
The campaign ran from January to March 2012 and encouraged people to tell their GP if they had 'blood in your poo or looser poo'.
Preliminary figures passed to GP show a 40% rise in GP urgent referrals for suspected lower GI cancer during the campaign. There were 43,690 referrals during February to April 2011 and 61,004 in the same period in 2012, when the campaign ran.
Bowel cancers detected via urgent referral rose 12%, from 2,580 to 2,877.
The £4m campaign was part of a DH drive to improve early diagnosis of cancer. Survival rates in England lag behind other major EU countries.
Bristol GP Dr Mike Cohen, whose practice hosts a community gastroenterology unit, said it was 'encouraging' to see more cancers diagnosed.
The unit recently detected colon cancer in a man in his thirties who had rectal bleeding for several months, with no other risk factors or family history. 'The campaign had encouraged him to see his GP,' said Dr Cohen.
Professor Stephen Duffy, a cancer screening expert at Queen Mary University of London, said the campaign showed it is possible to change patients' behaviour on cancer.
However, he cautioned: 'Whether that increase in cancers detected improved the stage of diagnosis enough to affect outcomes, I don't know. The jury is still out about whether this is the way to fix poorer survival.'
Dr Clare Gerada, RCGP chairwoman, said: 'Any improvement in cancer diagnosis is encouraging and these findings show that GPs take their responsibilities to refer patients, where there is a cause for concern, seriously.'
She said cancer was an 'enduring priority' for the college and had been working with Cancer Research UK and other partners to support GPs across the UK in cancer identification and referral.
The RCGP has organised e-learning courses, workshops and regional events on the subject.
Sara Hiom, director of patient engagement and early diagnosis at Cancer Research UK, said: 'It is essential that we continue to improve cancer survival in England, and evaluation of the campaigns is helping us understand how early diagnosis might contribute. Getting more people into the system sooner gives GPs a better opportunity to assess more patients.'
The DH recently announced Be Clear On Cancer programmes for 2013/14, including for bowel, lung, breast and ovarian cancers.