In what will be seen as a very unhelpful intervention to the debate on immigration by many church campaigners for the rights of migrants and refugees, the former Archbishop of Canterbury, George Carey, has called for a "clear cap" on population growth.

In comments given to today's News of the World he blamed an “open door policy on immigration” for the rise of the British National Party.

He also blamed a failure to "absorb" new communities and called for immigration to take centre stage at the next general election.

Many church campaigners have been deliberately pursing an alternative strategy that would avoid the issue becoming a political football at the time of the election.

Carey told the News of the World: “The cowardly failure of successive governments to address our open borders is the reason the BNP has gained admittance to the political mainstream.

“With the latest estimate that our population will rise by nearly 10 million by 2030, politicians are ducking the unpalatable truth: we are now one of the most over-populated countries in the world.”

“It is asking a huge amount of the British public to accept an open-door policy on immigration. They have seen a massive influx of newcomers, they have seen their jobs hit, and they feel ignored. There have not been adequate resources to help [the] community adapt to these massive changes.

"Yet it is not only a question of resources but the failure to absorb and integrate new communities. The discredited policy of multiculturalism must be abandoned once and for all. Now a controlled approach to immigration is needed with clear caps set on population growth. If the mainstream parties begin listening to the voters, the BNP can be consigned again to the fringes.

"Make no mistake about it, immigration must be a major item on next year's General Election agenda."

His comments came as he also urged Christians to unite against the BNP's claims to be a Christian party defending "Christian Britain."