Mass migration of Christians to Britain from countries such as Poland and Romania is among the factors helping to stem the decline in church attendance, according to new figures.

The latest analysis of church membership shows a growth in black-led churches and the mainstream churches' so-called "fresh expressions" movement have also helped curb the rate of decline.

The fall in church membership previously anticipated for 2020 will now not be evident until 2025, according to the research by Peter Brierley, whose second edition of UK Church Statistics, is due to be published soon.

Brierley said that the alleviation in the rate of decline was due partly to "the large number of new black and other immigrant churches which have been started" and "the increasing success of new gatherings" in the fresh expressions movement.

Fresh expressions has become a generic name for what Brierly describes as "fairly informal gatherings like "messy church", pub groups or café churches, mission-minded churches, Churches Without Walls (especially in Scotland) as well as those specifically named as fresh expressions".

Every one of nearly 300 Christian denominations in the UK was surveyed in mid-2013 and the results referenced against the 2011 census results with the questions on religion, ethnicity and immigration.

Brierley said: "Since many of the immigrants have come from 'Christian' countries, the flow of new people into existing congregations has been notable, as well as resulting in the formation of hundreds of new churches."

The black majority churches explosion has been significant, particularly in London, where of the 700 mostly Pentecostal new churches which began between 2005 and 2012, at least 400 were BMCs. The Redeemed Christian Church of God alone has started 296 new churches in the UK in the last 5 years, the largest number for any single denomination.

The main denominations boosted by the influx of immigrants are Roman Catholics mostly from Poland, the orthodox largely from Romania, the Pentecostals and the many overseas protestant churches that typically have roots in Africa.

Between them, these four major groups have more than 50 denominations dedicated to those from overseas countries, some countries having immigrant churches from multiple denominations, such as Polish Catholics and Polish Lutherans, or Romanian orthodox and Romanian Catholics.

The first volume of UK Church Statistics was based on research in 2010 and at that time the total UK church membership for 2015 was estimated as 5,190,000, and 2020 as 4,860,000. In this second volume these figures are estimated respectively as 5,370,000 and 5,040,000, with a 2025 forecast of 4,790,000, these being increases of nearly 4% on the previous 2015 and 2020 figures.

Brierley said: "While these increases are not sufficient to bring overall growth, these two key movements have, however, in effect, pushed the previous rate of decline back by about five years."

In 2011, 80% of English people classified themselves as white-British, which means that 20% came from other ethnic backgrounds. This compares to a decade earlier when English people were 88% white-British, meaning that the number of white-British people in England has actually decreased by 3.3 million people between the two census surveys, while the population as a whole has increased by 1 million.

In 2013, there were 5.4 million church members in the UK, 10% of the adult population, taken as 15 and over, 300,000 fewer than five years previously in 2008, when it was 12%. It is likely to continue to decline at about the same rate for the next 12 years, reaching 9% by 2020 and 8% by 2025, if present trends continue.