Prime Minister David Cameron has "done more than any other recent political leader" to "feed" anxiety among Christians, according to former Archbishop of Canterbury Lord Carey.
Writing in the Daily Mail, Lord Carey accused ministers of "aiding and abetting" discrimination against Christians.
He said many Christians doubted the Prime Minister's sincerity in promising protection for Christians practising their faith.
Sharp criticism was levelled at Mr Cameron for comments he made at a pre-Easter reception with religious leaders in which he had told them to "stand up and oppose aggressive secularisation".
It was "a bit rich" to hear the Prime Minister make such a plea, he said, when "it seems his government is aiding and abetting this aggression every step of the way".
Lord Carey went on to say he was "very suspicious" that behind the Government's plans to legalise gay marriage "there lurks an aggressive secularist and relativist approach towards an institution that has glued society".
His comments follow a new poll for the Coalition for Marriage in the run-up to Easter which found widespread feelings of marginalisation among Christians.
More than two thirds (67 per cent) of Christians surveyed by ComRes felt that they are part of a "persecuted minority" and almost eight in ten (77 per cent) say the PM's gay marriage plan will lead to those who back traditional marriage facing the sack.
Commenting on the poll, Lord Carey said: "Their fears are exaggerated because few in the UK are actually persecuted, but the Prime Minister has done more than any other recent political leader to feed these anxieties."