The third index, which will run alongside the RPI and the consumer prices index, will be the known as the RPIJ. It is hoped this new index will meet international standards and will apply from March 2013.
Jil Matheson, national statistician at the ONS, said there was "significant value to users in maintaining the continuity of the existing RPI's long-term series without major change". It would continue to be used for long-term indexation and for index-linked gilts and bonds.
Advisers had been concerned about the possibility of bringing the RPI into line with the CPI and the problems it could have caused pensions.
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Responses to the consultation, which ran from September to November 2012, recommended that no change was made to the measurements.
Ros Altmann, director-general at Saga said: "These indices are vital to many people's future income and, if they are being used as a way of providing protection against inflation, they need to reflect as well as possible the actual prices that people will face in the future.
"If the inflation measures being used are actually under-records inflation, then those whose incomes are meant to be protected will become poorer over time and be able to afford to buy less and less each year."

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