The British Humanist Association has launched a campaign to encourage non-believers and the seriously lapsed to tick the "no religion" box on the 2011 census with the aim of challenging religious privilege in Britain.

According to the organisation, public figures have spent the last 10 years claiming that most people in this country are religious to justify the money or attention spent on these communities.

While the statistics show that 37.3m people stated their religion as Christian, these figures are not reflected in church attendance.

The beef the BHA has with the census is manifold but, principally, it is that it underestimates the number of non-religious people and inflates the Christian population. The official figures show that in 2001 15.1% of respondents did not answer the religion question (which was voluntary) and 7.8% of the people who did said they had no religion.

That equates to 22.9% of respondents – approximately 13 million people – who were either non-religious, did not want to answer the question or failed to spot it. The no-religion group exceeded the Muslim, Jewish, Sikh and Hindu populations combined.

Since the last census was carried out, the BHA believes the numbers of the non-religious have increased. And there have been high-profile campaigns by atheists such as Richard Dawkins and the group behind the Atheist bus.

The BHA says it is time for people who never go to church or who never think about religion to 'fess up: " ... what people do not realise is that by ticking the 'Christian' box rather than the 'no religion' box – which would more accurately reflect their identity – they have contributed to data used to justify an increase in the number of 'faith' schools, the public funding of religious groups, keeping Bishops in the House of Lords as of right, and the continuation of compulsory worship in schools." Yes you fickle and lazy lot, the humanists blame you for all that.

While some might argue that humanists have no more place to tell you what to do than religious institutions, it will be interesting to see what difference a decade of high profile campaigning and posturing front has done to the thorny question of religious belief in Britain.