Not true, see below with the last census
The table below shows data regarding religion for the 2001 and 2011 censuses:
Religion 2001/2011
Christian 42,079,417 71.58% 37,583,962 59.49%
Muslim 1,591,126 2.71% 2,786,635 4.41%
Hindu 558,810 0.95% 835,394 1.32%
Sikh 336,149 0.57% 432,429 0.68%...