Vanguard has become the second platform member at the Association of British Insurers (ABI).
Platform membership is a new category established last year to reflect the changing nature of the long-term savings market and to deal with a growing focus among pension providers on improving transfers and re-registration in the wake of the pension flexibilities.
Sean Hagerty, head of Vanguard Europe, said: "Through its new membership category, the ABI has rightly identified that platforms are an increasingly important part of the market and will play a significant role in changing long-term saving and the way individuals save.
"The harsh reality is people are not saving enough for retirement. Our membership will enable us to support and help influence Government policy to encourage more people to save and invest for their future.
"As part of this, we believe investment providers must continue to lower the cost and complexity of investing. As an industry, we have a responsibility to make investing easier and less costly for investors."
Andy Briggs, chairman for ABI, said it opened its membership to platforms to reflect the increasingly important role they play in the long-term savings market, as technology is fundamentally changes how customers interact with their long-term saving choices.
He added: "The market is strongest when it speaks with one voice, and welcoming Vanguard into our membership will help us do just that."
Yvonne Braun, director of policy for long term savings and protection for ABI, said there have been sweeping changes in the world of long-term savings in the past few years, and the ABI is evolving to keep pace with those changes.
She added: "We already represent a significant part of the platform sector, through insurer-owned platforms and ABI platform member Hargreaves Lansdown.
"It is fantastic that we can now welcome investment platform Vanguard – this will strengthen our voice, so we can do the best possible job of representing the industry to Government and regulators, and putting savers at the heart of what we do."