Professor Woodhead told The Tablet that the Church of England clergy represented in these figures began to leave their original Church from 1994, when the first women were ordained priests. Those who left between 1994 and 2004 were provided with financial compensation amounting to 100 per cent of their stipend in year one, three-quarters in year two and two-thirds in year three. The payments amounted to £27.4 million over a decade.

She wanted to establish the veracity of reports that 400-500 priests and thousands of lay faithful had decided to join the Catholic Church, with many now serving as priests, including hundreds who are married.

She estimates that about 250 clergy "went across" between 1994 and 2000, with a further 52 from 2001, and then the Ordinariate clergy on top of that.

Professor Woodhead pointed out that the Catholic Church made the biggest gain from the moves given that there are 18,000 Anglican clergy compared with around 4,000 Catholic priests.

"So a relatively small loss of clergy numbers for the Church of England represents a very significant gift for the Catholic Church in England and Wales at a time of falling ordinations," she said.

Meanwhile, Mgr Keith Newton, the Ordinary, said in a homily at Portsmouth Cathedral that people sometimes asked members of the Ordinariate why they couldn't become "proper Catholics."

He said: "What they mean is, why can't you just be absorbed into the wider Catholic Church so that what you bring disappears like sugar dissolved in water," stressing that Christian unity was not about uniformity.

In September there will be events held by Ordinariate groups across the country to promote better understanding of the structure, set up to allow Anglicans to become Catholics while retaining elements of their identity

END