M&G, which demerged from Prudential in 2019, confirmed the takeover in a business update today.
Ascentric provides platform services to about 1,500 adviser firms covering over 90,000 clients and has been part of Royal London since 2007. Ascentric was one of the few parts of the business not to use the Royal London brand.
John Foley, M&G chief executive, said: "This deal strengthens our position in the UK savings and investment market, complementing our existing offering to advisers and customers with a well-established digital wealth management platform.
"Ascentric's platform will also accelerate our ability to provide a wider range of M&G and Prudential investment solutions to more customers, through the tax wrappers and service propositions they favour. Advisers will also benefit as we invest to grow the platform."
The acquisition brings to M&G a capability to offer third-party discretionary fund management services, as well as Individual Savings Account (ISA), Self-Invested Personal Pension (SIPP) and General Investment Account (GIA) wrappers on a single platform."
Speculation about Ascentric being sold off have been circulating for some time.
Ascentric re-platformed last year, moving to the Bravura system, a move that caused some planned non-availailability of services for several days and some criticism from advisers.
In June last year Royal London appointed experienced Standard Life exec Barry O’Dwyer as its chief executive to replace long term CEO Phil Loney.
The sale for an undisclosed sum follows a review of the business by Royal London chief executive, Barry O'Dwyer.
Mr O'Dwyer, said: "As part of our strategic review of the business, we explored a number of options for Ascentric. The business has been performing well following its re-platforming and we sought an outcome that would take it to its next phase of growth.
“We believe that a sale to M&G delivers this for Ascentric and I am pleased to have found a buyer who has a strong commitment to Ascentric's client and customer base and who is looking to further grow the business. I would like to thank the Ascentric team for their contribution to building a valuable business over the past years.
Rob Regan, chief executive of Ascentric, said: "This is a compelling transaction for Ascentric. It is very clear that M&G is aligned with our values and ethos and represents a good home for our advisers, strategic partners and staff. M&G is well-placed to take us on the next stage of our journey leveraging its scale to grow the business. We look forward to working with M&G to support our clients and customers going forward as well as through the transition from Royal London's ownership."
The deal is subject to regulatory approval.
• Editor's Note: Story updated 9.25 am to include M&G comment.