At least a million more Britons should be put on antidepressants, the authors of the largest ever review of the drugs today conclude.

The research led by Oxford University, and published in The Lancet, examined 522 trials involving 21 types of medication over almost four decades.

All were found to be effective, yet its authors warned that just one in six patients suffering from depression are receiving treatment.

Researchers said too many GPs were “squeamish” about offering medication for depression, when they would not hesitate to ensure patients received treatment for cancer or heart disease.

The findings also constitute the first ever league tables comparing different antidepressants.

Some of the best known antidepressants in Britain - such as Prozac - and the most widely prescribed drug, citalopram - were found to be among the least effective.