Mr Webb told MPs yesterday on the Commons Scottish Affairs Committee that pensioners had "accumulated rights".
But he suggested that how pensioners received that money would still be a matter for negotiation in the event of a Yes vote.
He warned that the average worker would have to pay an extra £200 a year to fund the pension plans contained in Scottish ministers' White Paper.
The Scottish Government said his words provided confirmation that state pensions would be "entirely secure" after independence.
Mr Webb told MPs: "Citizenship is irrelevant. It is what you have put into the UK National Insurance system prior to separation. Answer 35 years, that builds up to a continued UK pension under continuing UK rules. They are entitled to that money."
He added: "Take a Scottish person who works all their life and then retires to France...they still have an accumulated pension right in respect of the NI they have paid in when they were part of the United Kingdom."
A spokesman for Finance Secretary John Swinney said: "This is confirmation that people's pensions will be entirely secure following a Yes vote."