Dr Altmann said it was time to get more directly involved to help consumers as The Prime Minister announced she would be made a Minister.
She is to be nominated as a Conservative peer.
Her role would be leading a review of financial consumer protection and financial education.
Mr Cameron said: "What we're doing is taking the country's leading expert on pensions, on savings, on financial education, Ros Altmann, and saying that if we're re-elected, she'll be at the heart of government, making sure we complete this great revolution where we're giving people much more power to save, to access their pension, to pass their pension on to their children, because we want to create a real savings culture in our country for everybody.
"Not for the rich at the top, but for everybody who saves or has a pension."
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Dr Altmann said: "I truly believe most British savers will be responsible and can be trusted to make the right choices. They will need protection, they will need guidance and many will also need advice, but that is where I hope I can make a difference.
"It will be my job to review this and ensure customers get a fair deal – I am delighted to be offered the chance to do so."
She said: "I want to see long-term savings work better for ordinary families who put their hard-earned savings aside for their future, which is so important to restoring the strong British savings culture. Those with the largest pension savings already had the freedoms and flexibility that are now open to everyone, but of course we must ensure financial services firms move with the times.
"This will mean a new mindset from providers and potentially further Government action to protect savers better.
"Of course it won't be easy, but I'm determined to make a difference."
She believes she can be more effective working with the industry to adapt to the new environment from within Government.
She added: "I will also continue to champion the need for fairness and inclusiveness for women and for customers of all ages – which is where I believe financial education and guidance can be particularly powerful."
Tom McPhail, head of pensions research at Hargreaves Lansdown, said: "We have mixed feelings about this announcement. Ros has a strong reputation for speaking up on behalf of consumers on matters of personal finance, in particular on pensions.
"However her remit will cover consumer protection and financial education, tasks which are already performed by organisations such as the Financial Conduct Authority and the Money Advice Service. "The key priority and principle measure of success for any savings and investment minister should be encouraging more people to save and invest. Unfortunately this essential objective is still not being taken seriously enough by any of the political parties, and it does not seem to be within the scope of this role either."